query: where does meiosis occur in plants and animals

pos: Meiosis of chromosomes as the original parent cell. The two meiotic divisions are known as Meiosis I and Meiosis II. Before meiosis begins, during S phase of the cell cycle, the DNA of each chromosome is replicated so that it consists of two identical sister chromatids, which remain held together through sister chromatid cohesion. This S-phase can be referred to as "premeiotic S-phase" or "meiotic S-phase". Immediately following DNA replication, meiotic cells enter a prolonged G2-like stage known as meiotic prophase. During this time, homologous chromosomes pair with each other and undergo genetic recombination, a programmed process in which DNA is

pos: Meiosis Meiosis Meiosis (; from Greek μείωσις, "meiosis", which means lessening) is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them. This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants, and fungi. Errors in meiosis resulting in aneuploidy are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number

pos: Cell (biology) the S phase of the cell cycle. In meiosis, the DNA is replicated only once, while the cell divides twice. DNA replication only occurs before meiosis I. DNA replication does not occur when the cells divide the second time, in meiosis II. Replication, like all cellular activities, requires specialized proteins for carrying out the job. Between successive cell divisions, cells grow through the functioning of cellular metabolism. Cell metabolism is the process by which individual cells process nutrient molecules. Metabolism has two distinct divisions: catabolism, in which the cell breaks down complex molecules to produce energy and reducing power, and

neg: Sexual reproduction embryos. Animals typically produce gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization follows immediately after meiosis. Plants on the other hand have mitosis occurring in spores, which are produced by meiosis. The spores germinate into the gametophyte phase. The gametophytes of different groups of plants vary in size; angiosperms have as few as three cells in pollen, and mosses and other so called primitive plants may have several million cells. Plants have an alternation of generations where the sporophyte phase is succeeded by the gametophyte phase. The sporophyte

neg: Sexual selection in fungi a haploid-diploid life cycle. Sexual selection is much more crucial in the diploid phase as the product of the phase immediately undergoes meiosis and can no longer be fertilized again. Competition can occur within fungi as it does in plants and animals if an inequality in the ability to access one sex role or mating type is present. This inequality could result in increased competition for access to the other mating type. Competition can also occur if there is a variation in the quality of the gametes. Within fungi, there is competition to fertilize, which can be seen as the

neg: Meiosis two identical daughter cells. In some plants, fungi, and protists meiosis results in the formation of spores: haploid cells that can divide vegetatively without undergoing fertilization. Some eukaryotes, like bdelloid rotifers, do not have the ability to carry out meiosis and have acquired the ability to reproduce by parthenogenesis. Meiosis does not occur in archaea or bacteria, which generally reproduce asexually via binary fission. However, a "sexual" process known as horizontal gene transfer involves the transfer of DNA from one bacterium or archaeon to another and recombination of these DNA molecules of different parental origin. Meiosis was discovered and described

neg: Asexual reproduction some protists, who undergo "meiosis" immediately followed by fertilization. Plants and many algae on the other hand undergo "sporic meiosis" where meiosis leads to the formation of haploid spores rather than gametes. These spores grow into multi-cellular individuals (called gametophytes in the case of plants) without a fertilization event. These haploid individuals give rise to gametes through mitosis. Meiosis and gamete formation therefore occur in separate generations or "phases" of the life cycle, referred to as alternation of generations. Since sexual reproduction is often more narrowly defined as the fusion of gametes (fertilization), spore formation in plant sporophytes and algae

neg: Meiosis haploid organism's gamete, creating the zygote. The zygote undergoes repeated mitosis and differentiation to become a diploid organism again. The haplodiplontic life cycle can be considered a fusion of the diplontic and haplontic life cycles. Meiosis occurs in all animals and plants. The end result, the production of gametes with half the number of chromosomes as the parent cell, is the same, but the detailed process is different. In animals, meiosis produces gametes directly. In land plants and some algae, there is an alternation of generations such that meiosis in the diploid sporophyte generation produces haploid spores. These spores multiply

neg: Homologous recombination plants, animals, fungi and protists. In cells that divide through mitosis, homologous recombination repairs double-strand breaks in DNA caused by ionizing radiation or DNA-damaging chemicals. Left unrepaired, these double-strand breaks can cause large-scale rearrangement of chromosomes in somatic cells, which can in turn lead to cancer. In addition to repairing DNA, homologous recombination also helps produce genetic diversity when cells divide in meiosis to become specialized gamete cells—sperm or egg cells in animals, pollen or ovules in plants, and spores in fungi. It does so by facilitating chromosomal crossover, in which regions of similar but not identical DNA are exchanged

neg: Oogenesis maturity. In plants, oogenesis occurs inside the female gametophyte via mitosis. In many plants such as bryophytes, ferns, and gymnosperms, egg cells are formed in archegonia. In flowering plants, the female gametophyte has been reduced to an eight-celled embryo sac within the ovule inside the ovary of the flower. Oogenesis occurs within the embryo sac and leads to the formation of a single egg cell per ovule. In "ascaris", the oocyte does not even begin meiosis until the sperm touches it, in contrast to mammals, where meiosis is completed in the estrus cycle. Oogenesis Oogenesis, ovogenesis, or oögenesis is the

neg: Gametangium Gametangium A gametangium (plural: gametangia) is an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis. Depending on the type of gamete produced in a gametangium, several types can be distinguished. Female gametangia are most commonly called archegonia. They produce egg cells and are the sites for fertilization. Archegonia are common in algae and primitive plants as well as gymnosperms. In flowering plants, they are replaced by

neg: Oogenesis occurs and tetrads form, enabling chromosomal crossover to occur. As a result of meiosis I, the primary oocyte has now developed into the secondary oocyte and the first polar body. Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II. However, this process is also halted at the metaphase II stage until fertilization, if such should ever occur. If the egg is not fertilized, it is disintegrated and released (menstruation) and the secondary oocyte does not complete meiosis II (and doesn't become an ovum). When meiosis II has completed, an ootid and another polar body have now been created.

neg: Meiosis by mitosis, developing into the haploid gametophyte generation, which then gives rise to gametes directly (i.e. without further meiosis). In both animals and plants, the final stage is for the gametes to fuse, restoring the original number of chromosomes. In females, meiosis occurs in cells known as oocytes (singular: oocyte). Each primary oocyte divides twice in meiosis, unequally in each case. The first division produces a daughter cell, and a much smaller polar body which may or may not undergo a second division. In meiosis II, division of the daughter cell produces a second polar body, and a single haploid

neg: Panama disease thus attempts at meiosis in the plant's ovules cannot produce a viable gamete. Only rarely does the first reduction division in meiosis in the plants' flowers tidily fail completely, resulting in a euploid triploid ovule, which can be fertilized by normal haploid pollen from a diploid banana variety; a whole stem of bananas would contain only a few seeds and sometimes none. As a result, the resulting new banana variety is tetraploid, and thus contains seeds; the market for bananas is not accustomed to bananas with seeds. Experience showed that where both meiosis steps failed, causing a heptaploid seedling, or

neg: Hellebore still to be proven. The following hellebore species and cultivars have gained the Royal Horticultural Society's Award of Garden Merit:- All helleborus plants are toxic, and all parts of the helleborus plant are toxic. Hellebore poisoning is rare, but it does occur. Hellebore plants are usually left alone by animals such as deer and rabbits due to the fact that the leaves of the plant produce poisonous alkaloids, making them distasteful to animals. The poisonous alkaloids have been known to sometimes bother gardeners with sensitive skin. Poisonings will occur through ingestion or handling. Hellebore plants should not be ingested as

neg: Sexual reproduction Sexual reproduction Sexual reproduction is a kind of life cycle where generations alternate between cells with a single set of chromosomes (haploid) and cells with a double set of chromosomes (diploid). "Sexual reproduction" is by far the most common life cycle in eukaryotes, for example animals and plants. Diploid cells divide into haploid cells in a process called meiosis. Two haploid cells combine into one diploid cell in a process called fertilisation. Between fertilisation and meiosis there can be a large number of cell divisions without change of the number of chromosomes. Fertilization creates a single-celled zygote which includes genetic

neg: Asexual reproduction of seeds or spores by meiosis or syngamy. Examples of vegetative reproduction include the formation of miniaturized plants called plantlets on specialized leaves (for example in kalanchoe) and some produce new plants out of rhizomes or stolon (for example in strawberry). Other plants reproduce by forming bulbs or tubers (for example tulip bulbs and dahlia tubers). Some plants produce adventitious shoots and may form a clonal colony, where all the individuals are clones, and the clones may cover a large area. Many multi-cellular organisms form spores during their biological life cycle in a process called sporogenesis. Exceptions are animals and

neg: Origin and function of meiosis the adaptive advantage of sex. Origin and function of meiosis <onlyinclude>The origin and function of meiosis are fundamental to understanding the evolution of sexual reproduction in eukaryotes. There is no current consensus among biologists on the questions of how sex in eukaryotes arose in evolution, what basic function sexual reproduction serves, and why it is maintained, given the basic two-fold cost of sex. It is clear that it evolved over 1.2 billion years ago, and that almost all species which are descendants of the original sexually reproducing species are still sexual reproducers, including plants, fungi, and animals. Meiosis is a

neg: Origin and function of meiosis Origin and function of meiosis <onlyinclude>The origin and function of meiosis are fundamental to understanding the evolution of sexual reproduction in eukaryotes. There is no current consensus among biologists on the questions of how sex in eukaryotes arose in evolution, what basic function sexual reproduction serves, and why it is maintained, given the basic two-fold cost of sex. It is clear that it evolved over 1.2 billion years ago, and that almost all species which are descendants of the original sexually reproducing species are still sexual reproducers, including plants, fungi, and animals. Meiosis is a key event of the sexual

neg: Asexual reproduction as that of the parent producing the spores. However, mitotic sporogenesis is an exception and most spores, such as those of plants, most Basidiomycota, and many algae, are produced by meiosis. Fragmentation is a form of asexual reproduction where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. Fragmentation is seen in many organisms. Animals that reproduce asexually include planarians, many annelid worms including polychaetes and some oligochaetes, turbellarians and sea stars. Many fungi and plants reproduce asexually. Some plants have specialized structures for reproduction via fragmentation, such as "gemma"

neg: Evolution two related species to produce a new hybrid species. This is not common in animals as animal hybrids are usually sterile. This is because during meiosis the homologous chromosomes from each parent are from different species and cannot successfully pair. However, it is more common in plants because plants often double their number of chromosomes, to form polyploids. This allows the chromosomes from each parental species to form matching pairs during meiosis, since each parent's chromosomes are represented by a pair already. An example of such a speciation event is when the plant species "Arabidopsis thaliana" and "Arabidopsis arenosa" crossbred

neg: Sporogenesis called spore mother cells) undergoing cell division to give rise to spores. In meiotic sporogenesis, a diploid spore mother cell within the sporangium undergoes meiosis, producing a tetrad of haploid spores. In organisms that are heterosporous, two types of spores occur: Microsporangia produce male microspores, and megasporangia produce female megaspores. In megasporogenesis, often three of the four spores degenerate after meiosis, whereas in microsporogenesis all four microspores survive. In gymnosperms, such as conifers, microspores are produced through meiosis from microsporocytes in microstrobili or male cones. In flowering plants, microspores are produced in the anthers of flowers. Each anther contains four

neg: Megaspore mother cell proteins regulate female meiosis by modulating meiotic gene expression in the megaspore mother cell. One of the key genes whose expression is regulated is "Dmc1", a gene that plays a central role in the strand-exchange reactions of meiotic recombinational repair. Megaspore mother cell A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes (megagametophytes). The megaspore mother cell arises within the megasporangium tissue. In flowering plants the megasporangium is also called the nucellus, and

neg: Gametogenesis Gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations. Animals produce gametes directly through meiosis in organs called gonads (testis in males

neg: Biological life cycle known as intermediary meiosis), the zygote divides mitotically to produce a multicellular diploid sporophyte. The sporophyte creates spores via meiosis which "also" then divide mitotically producing haploid individuals called gametophytes. The gametophytes produce gametes via mitosis. In some plants the gametophyte is not only small-sized but also short-lived; in other plants and many algae, the gametophyte is the "dominant" stage of the life cycle. Haplodiplonts are: Some animals have a sex-determination system called haplodiploid, but this is not related to the haplodiplontic life cycle. Some red algae (such as "Bonnemaisonia" and "Lemanea") and green algae (such as "Prasiola") have vegetative

neg: Paleopolyploidy an environment where autopolyploidy is very likely. This fact can be exploited in a laboratory setting by using colchicine to inhibit chromosome segregation during meiosis, creating synthetic autopolyploid plants. Following polyploidy events, there are several possible fates for duplicated genes; both copies may be retained as functional genes, change in gene function may occur in one or both copies, gene silencing may mask one or both copies, or complete gene loss may occur. Polyploidy events will result in higher levels of heterozygosity, and, over time, can lead to an increase in the total number of functional genes in the genome.

neg: Gametangium the gametes look alike and cannot be classified into "male" or "female." For example, in zygomycetes, two gametangia (single multinucleate cells at the end of hyphae) form good contact with each other and fuse into a zygosporangium. Inside the zygosporangium, the nuclei from each of the original two gametangia pair up. Gametangium A gametangium (plural: gametangia) is an organ or cell in which gametes are produced that is found in many multicellular protists, algae, fungi, and the gametophytes of plants. In contrast to gametogenesis in animals, a gametangium is a haploid structure and formation of gametes does not involve meiosis.

neg: Preprophase Preprophase Preprophase is an additional phase during mitosis in plant cells that does not occur in other eukaryotes such as animals or fungi. It precedes prophase and is characterized by two distinct events: Plant cells are fixed with regards to their neighbor cells within the tissues they are growing in. In contrast to animals where certain cells can migrate within the embryo to form new tissues, the seedlings of higher plants grow entirely based on the orientation of cell division and subsequent elongation and differentiation of cells within their cell walls. Therefore, the accurate control of cell division planes and

neg: Lycium barbarum embryo. The plants are self-pollinating, but may be cross pollinated by insects. The species is dispersed into natural areas by birds and other animals that eat its fruit. In the Northern Hemisphere, flowering occurs from June through September and berry maturation from August to October, depending on the latitude, altitude, and climate. Where frost does not occur fruiting is continuous and plants do not lose their leaves. "Lycium barbarum" has been cultivated in China, along the fertile aggradational floodplains of the Yellow River, for more than 600 years. It is still extensively cultivated in the Ningxia Hui Autonomous Region of

neg: Alternation of generations is maintained. The diagram above shows the fundamental elements of the alternation of generations in plants. The many variations found in different groups of plants are described by use of these concepts later in the article. Starting from the right of the diagram, the processes involved are as follows: The 'alternation of generations' in the life cycle is thus between a diploid (2"n") generation of sporophytes and a haploid ("n") generation of gametophytes. The situation is quite different from that in animals, where the fundamental process is that a diploid (2"n") individual directly produces haploid ("n") gametes by meiosis. Spores

neg: Homologous chromosome the same in mitosis as they do in meiosis. Prior to every single mitotic division a cell undergoes, the chromosomes in the parent cell replicate themselves. The homologous chromosomes within the cell will ordinarily not pair up and undergo genetic recombination with each other. Instead, the replicants, or sister chromatids, will line up along the metaphase plate and then separate in the same way as meiosis II - by being pulled apart at their centromeres by nuclear mitotic spindles. If any crossing over does occur between sister chromatids during mitosis, it does not produce any new recombinant genotypes. Homologous pairing

neg: Germ cell Germ cell A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult (such as the floral meristem of flowering plants). Multicellular eukaryotes are made of two fundamental cell types. Germ

neg: Pseudoautosomal region they allow the X and Y chromosomes to pair and properly segregate during meiosis in males. Pseudoautosomal genes are found in two different locations: PAR1 and PAR2. These are believed to have evolved independently. in mice, some PAR1 genes have transferred to autosomes. Pairing (synapsis) of the X and Y chromosomes and crossing over (recombination) between their pseudoautosomal regions appear to be necessary for the normal progression of male meiosis. Thus, those cells in which X-Y recombination does not occur will fail to complete meiosis. Structural and/or genetic dissimilarity (due to hybridization or mutation) between the pseudoautosomal regions of the

neg: Glucose are termed glucans. Glucose is produced by plants through the photosynthesis using sunlight, water and carbon dioxide and can be used by all living organisms as an energy and carbon source. However, most glucose does not occur in its free form, but in the form of its polymers, i.e. lactose, sucrose, starch and others which are energy reserve substances, and cellulose and chitin, which are components of the cell wall in plants or fungi and arthropods, respectively. These polymers are degraded to glucose during food intake by animals, fungi and bacteria using enzymes. All animals are also able to produce

neg: Microsporangia wall layers from periphery to center consist of: Microsporangia Microsporangia are sporangia that produce microspores and give rise to male gametes. Microsporangia occur in all plants that have heterosporic life cycles, such as spike mosses. In gymnosperms and angiosperm anthers, the microsporangia produce the microsporocytes, the microspore mother cells, which then produce four microspores through the process of meiosis. In the microsporocyte of "Arabidopsis thaliana", meiosis depends on the expression of genes that facilitate DNA repair and homologous recombination. The microspores divide by mitosis to produce pollen grains. In angiosperms, a very young anther (the part of the stamen that

neg: Microsporangia Microsporangia Microsporangia are sporangia that produce microspores and give rise to male gametes. Microsporangia occur in all plants that have heterosporic life cycles, such as spike mosses. In gymnosperms and angiosperm anthers, the microsporangia produce the microsporocytes, the microspore mother cells, which then produce four microspores through the process of meiosis. In the microsporocyte of "Arabidopsis thaliana", meiosis depends on the expression of genes that facilitate DNA repair and homologous recombination. The microspores divide by mitosis to produce pollen grains. In angiosperms, a very young anther (the part of the stamen that contains the pollen) consists of actively dividing meristematic

neg: Parthenogenesis (e.g., aphids) while the production of males by parthenogenesis is referred to as arrhenotoky (e.g., bees). When unfertilized eggs develop into both males and females, the phenomenon is called deuterotoky. Parthenogenesis can occur without meiosis through mitotic oogenesis. This is called "apomictic parthenogenesis". Mature egg cells are produced by mitotic divisions, and these cells directly develop into embryos. In flowering plants, cells of the gametophyte can undergo this process. The offspring produced by apomictic parthenogenesis are "full clones" of their mother. Examples include aphids. Parthenogenesis involving meiosis is more complicated. In some cases, the offspring are haploid (e.g., male ants).

neg: Complementation (genetics) molecular machines are constructed. Heterosis is the tendency for hybrid individuals to exceed their pure bred parents in size and vigor. The phenomenon has long been known in animals and plants. Heterosis appears to be largely due to genetic complementation, that is the masking of deleterious recessive alleles in hybrid individuals. In general, the two fundamental aspects of sexual reproduction in eukaryotes are meiosis, and outcrossing. These two aspects have been proposed to have two natural selective advantages, respectively. Meiosis is proposed to be adaptive because it facilitates recombinational repair of DNA damages that are otherwise difficult to repair. Outcrossing

neg: Cdc14 abnormally. The abnormality arises due to delay in dissembling of spindle during Anaphase I. However, the segregation of chromosomes continue and both the phases of meiotic segregations take place on prolonged meiosis I spindle. Cdc14 along with SPO12 and SLK19 play a critical role in ensuring that the two phases of chromosomal segregation take place consecutively during meiosis. Cdc14 is widely distributed, being found in most eukaryote kingdoms. However, it is not found in all species based on searches of sequenced genomes. One or more Cdc14 genes are found in alveolates, animals, fungi, trypanosomes, and lower plants. However, Cdc14 genes

neg: Polyploidy defined with respect to a cell. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Male bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis, the sporophyte generation is diploid and produces spores by meiosis. Polyploidy refers to a numerical change in a whole set of chromosomes. Organisms

neg: Botany several methods used by plants to promote outcrossing. In many land plants the male and female gametes are produced by separate individuals. These species are said to be dioecious when referring to vascular plant sporophytes and dioicous when referring to bryophyte gametophytes. Unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. The formation of stem tubers in potato is one example. Particularly in arctic or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction

neg: Fin Fin on Teo the Magic Planet various animals and plants in the Planet TEO. Some plants only appear at night, ans some only at day. Some animals are friendly to Finfin, while others want to eat him (but they never can). The game includes natural weather, from sunny days to cloudy days, rain or even thunderstorms. However, snowfall does not occur in the game because the areas in the game are close to the equator and so the temperatures are constantly in the warm to mild range. In addition to the weather, there are also annual events such as shooting stars and lunar eclipses, and natural

neg: Homologous recombination as a eukaryote, suggests that meiotic homologous recombination—and thus meiosis itself—emerged very early in eukaryotic evolution. In addition to research on Dmc1, studies on the Spo11 protein have provided information on the origins of meiotic recombination. Spo11, a type II topoisomerase, can initiate homologous recombination in meiosis by making targeted double-strand breaks in DNA. Phylogenetic trees based on the sequence of genes similar to SPO11 in animals, fungi, plants, protists and archaea have led scientists to believe that the version Spo11 currently in eukaryotes emerged in the last common ancestor of eukaryotes and archaea. Many methods for introducing DNA sequences

neg: Desert water in the form of springs and seepages from aquifers. Where these are found, oases can occur. Plants and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles and often spines to deter herbivory. Some annual plants germinate, bloom and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to keep cool and find enough food and water to survive. Many

neg: Megaspore mother cell Megaspore mother cell A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes (megagametophytes). The megaspore mother cell arises within the megasporangium tissue. In flowering plants the megasporangium is also called the nucellus, and the female gametophyte is sometimes called the embryo sac. Two distinct processes are involved in producing the megagametophyte from the megaspore mother cell: In gymnosperms and most flowering plants, only one of the four megaspores is functional at maturity, and

neg: Sexual reproduction phase produces spores within the sporangium by meiosis. Flowering plants are the dominant plant form on land and they reproduce either sexually or asexually. Often their most distinguishing feature is their reproductive organs, commonly called flowers. The anther produces pollen grains which contain the male gametophytes (sperm). For pollination to occur, pollen grains must attach to the stigma of the female reproductive structure (carpel), where the female gametophytes (ovules) are located inside the ovary. After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell

neg: Bud and described according to different criteria: location, status, morphology, and function. Botanists commonly use the following terms: The term bud (as in budding) is used by analogy within zoology as well, where it refers to an outgrowth from the body which develops into a new individual. It is a form of asexual reproduction limited to animals or plants of relatively simple structure. In this process a portion of the wall of the parent cell softens and pushes out. The protuberance thus formed enlarges rapidly while at this time the nucleus of the parent cell divides (see: mitosis, meiosis). One of

neg: Fungus maydis" has a well-established recombinational DNA repair system which acts during mitosis and meiosis. The system may assist the pathogen in surviving DNA damage arising from the host plant’s oxidative defensive response to infection. "Cryptococcus neoformans" is an encapsulated yeast that can live in both plants and animals. "C. neoformans" usually infects the lungs, where it is phagocytosed by alveolar macrophages. Some "C. neoformans" can survive inside macrophages, which appears to be the basis for latency, disseminated disease, and resistance to antifungal agents. One mechanism by which "C. neoformans" survives the hostile macrophage environment is by up-regulating the expression of

neg: Plant reproduction spores by meiosis, sometimes referred to as "reduction division" because the chromosome pairs are separated once again to form single sets. In mosses and liverworts the gametophyte is relatively large, and the sporophyte is a much smaller structure that is never separated from the gametophyte. In ferns, gymnosperms, and flowering plants (angiosperms), the gametophytes are relatively small and the sporophyte is much larger. In gymnosperms and flowering plants the mega gametophyte is contained within the ovule (that may develop into a seed) and the micro gametophyte is contained within a pollen grain. Unlike animals, plants are immobile, and cannot seek

neg: Mucor a new mycelium on appropriate substrates. During sexual reproduction, compatible strains form short, specialized hyphae called gametangia. At the point where two complementary gametangia fuse, a thick-walled, spherical zygosporangium develops. The zygosporangium typically contains a single zygospore. Nuclear karyogamy and meiosis (sexual recombination) occur within the zygospores, which are thought to be long-lived and resistant to adverse conditions. They may germinate to form hyphae or a sporangium. "Mucor" includes both homothallic (self-compatible) and heterothallic species. Most species of 'Mucor' are unable to infect humans and endothermic animals due to their inability to grow in warm environments close to 37 degrees.

neg: Brachymeiosis Brachymeiosis Brachymeiosis was a hypothesized irregularity in the sexual reproduction of ascomycete fungi, a variant of meiosis following an "extra" karyogamy (nuclear fusion) step. The hypothesized process would have transformed four diploid nuclei into eight haploid ones. The current scientific consensus is that brachymeiosis does not occur in any fungi. According to the current understanding, ascomycetes reproduce by forming male and female organs (antheridia/spermatia and ascogonia), transferring haploid nuclei from the antheridium to the ascogonium, and growing a dikaryotic ascus containing both nuclei. Karyogamy then occurs in the ascus to form a diploid nucleus, followed by meiosis and mitosis to

neg: Polo-like kinase Plks contribute to the control of APC activity. Plk1 associates with kinetochores during mitosis. In the absence of Plk1 function, bipolar spindle formation does not occur and cells arrest in prometaphase owing to Spindle Assembly Checkpoint activation. Plk1 function may be important for relieving the inhibitory checkpoint signal. If so, Plk1 could contribute to the resumption of mitotic progression on complete attachment of all chromosomes to the spindle apparatus. The fly and yeast models have revealed that Polo kinases coordinate the more complex pattern of chromosome segregation in meiosis. Budding yeast Cdc5 is required in meiosis I for the removal

neg: Gametophyte function of which is to produce haploid spores by meiosis. In some multicellular green algae ("Ulva lactuca" is one example), red algae and brown algae, sporophytes and gametophytes may be externally indistinguishable (isomorphic). In "Ulva" the gametes are isogamous, all of one size, shape and general morphology. In land plants, anisogamy is universal. As in animals, female and male gametes are called, respectively, "eggs" and "sperm." In extant land plants, either the sporophyte or the gametophyte may be reduced (heteromorphic). In bryophytes (mosses, liverworts, and hornworts), the gametophyte is the most visible stage of the life cycle. The bryophyte gametophyte

neg: Genetic memory (biology) explain the inheritance of evolutionary changes. In ethology, genetic memory refers the inheritance of instinct in animals. Genetic memory (biology) In biology, memory is present if the state of a biological system depends on its history in addition to present conditions. If this memory is recorded in the genetic material and stably inherited through cell division (mitosis or meiosis), it is genetic memory. "Somatic memory" is limited to the organism and not passed on to subsequent generations. However, its mechanism may involve mitotically stable genetic memory. The term applies for cellular memory, animals' memory, and plants' memory, as described in

neg: Transgenerational epigenetic inheritance within cells is reset during meiosis (e.g. marks at the FLC locus controlling plant vernalization), though some epigenetic responses have been shown to be conserved (e.g. transposon methylation in plants). Differential inheritance of epigenetic marks due to underlying maternal or paternal biases in removal or retention mechanisms may lead to the assignment of epigenetic causation to some parent of origin effects in animals and plants. In mammals, epigenetic marks are erased during two phases of the life cycle. Firstly just after fertilization and secondly, in the developing primordial germ cells, the precursors to future gametes. During fertilization the male and

neg: Speciation achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered an extremely rare event. The Mariana mallard is thought to have arisen from hybrid speciation. Hybridization is an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals. Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. Polyploids also have

neg: Autogamy plant. While the latter method does blur the lines between autogamous self-fertilization and normal sexual reproduction, it is still considered autogamous self-fertilization. Self-pollination can lead to inbreeding depression due to expression of deleterious recessive mutations. Meiosis followed by self-pollination results in little genetic variation, raising the question of how meiosis in self-pollinating plants is adaptively maintained over an extended period in preference to a less complicated and less costly asexual ameiotic process for producing progeny. For instance, "Arabidopsis thaliana" is a predominantly self-pollinating plant that has an outcrossing rate in the wild estimated at less than 0.3%, and self-pollination appears

neg: Microevolution however, an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals. Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. Polyploid hybrids also have more genetic diversity, which allows them to avoid inbreeding depression in small populations. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. In medicine, this

neg: Anaphase lag Anaphase lag Anaphase lag is a consequence of an event during cell division where sister chromatids do not properly separate from each other because of improper spindle formation. The chromosome or chromatid does not properly migrate during anaphase and the daughter cells will lose some genetic information. It is one of many causes of aneuploidy. This event can occur during both meiosis and mitosis with unique repercussions. In either case, anaphase lag will cause one daughter cell to receive a complete set of chromosomes while the other lacks one paired set of chromosomes, creating a form of monosomy. Whether the

neg: Ecological forecasting and climate can lead to large changes in the growth, reproduction and survival of animals and plants. The scientific consensus is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era. These changes are in turn affecting human and natural ecosystems. One major challenge is to predict where, when and with what magnitude changes are likely to occur so that we can mitigate or at least prepare for them. Ecological forecasting applies existing knowledge of how animals and plants interact with their physical environment to ask

neg: Thistle with crops and interference with grazing in pastures, where dense growths of spiny vegetation suppress forage plants and repel grazing animals from eating either the thistle plants or neighbouring forage. Some species, although not intensely poisonous, do affect the health of animals that swallow more than small amounts of the material. Conversely however, the genus "Cynara" includes commercially important species of artichoke and some species regarded as major weeds are commercial sources of vegetable rennet used in commercial cheese making. Similarly, some species of "Silybum" that occur as weeds, also are cultivated for seeds that yield vegetable oil and pharmaceutical

neg: Cell division the amount of cyclin increases, more and more cyclin dependent kinases attach to cyclin signaling the cell further into interphase. The peak of the cyclin attached to the cyclin dependent kinases this system pushes the cell out of interphase and into the M phase, where mitosis, meiosis, and cytokinesis occur. There are three transition checkpoints the cell goes through before entering the M phase. The most important being the G1-S transition checkpoint. If the cell does not pass this phase, then the cell will most likely not go through the rest of the cell division cycle. Prophase is the first

neg: Evidence of common descent is achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered a rare event. However, hybridization resulting in reproductive isolation is considered an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals. Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. Polyploids also have more genetic diversity, which allows

neg: Meiosis of the male testis suppress meiosis by degrading retinoic acid, a stimulator of meiosis. This is overcome at puberty when cells within seminiferous tubules called Sertoli cells start making their own retinoic acid. The normal separation of chromosomes in meiosis I or sister chromatids in meiosis II is termed "disjunction". When the segregation is not normal, it is called "nondisjunction". This results in the production of gametes which have either too many or too few of a particular chromosome, and is a common mechanism for trisomy or monosomy. Nondisjunction can occur in the meiosis I or meiosis II, phases of

neg: Epigenetics of human development that imprinting may help protect the female from ovarian trophoblastic disease and parthenogenesis. Trophoblastic disease occurs when a sperm fertilizes an egg with no nucleus and a cancer-like mass forms in the placenta. Parthenogenesis occurs when an unfertilized egg develops into a fully functional organism that is genetically identical to the parent, who is female in the case of animals or both sexes, in the case of plants. This does not occur naturally in mammals. In most animals, especially mammals, uniparental inheritance of chromosomes is often lethal or results in developmental abnormalities, sometimes physically but often cognitively. Other hypotheses point

neg: Paraptosis death. IGF-1R is an important area of research for neurodegenerative diseases, as defects in IGF-1R siginaling, including increased levels of IGF-1R, have been found in the brains of Alzheimer's patients. Paraptosis-like programmed cell death has been observed in both plants and protists. Apoptotic death similar to that found in animals does not occur in plants, due to the cell wall of plant cells preventing phagocytosis. In an experiment with tobacco, bleomycin was used to introduce double strand breaks in the cells' DNA. This then caused cells to undergo programmed cell death with considerable vacuolization and an absence of DNA fragmentation

neg: Zygote haploid cells is called karyogamy. The result of karyogamy is the formation of a diploid cell called zygote or zygospore. This cell may then enter meiosis or mitosis depending on the life cycle of the species. In plants, the zygote may be polyploid if fertilization occurs between meiotically unreduced gametes. In land plants, the zygote is formed within a chamber called the archegonium. In seedless plants, the archegonium is usually flask-shaped, with a long hollow neck through which the sperm cell enters. As the zygote divides and grows, it does so inside the archegonium. In human fertilization, a released ovum

neg: Selfish genetic element encompasses all of them is segregation distortion. Some elements can preferentially be transmitted in egg cells as opposed to polar bodies during meiosis, where only the former will be fertilized and transmitted to the next generation. Any gene that can manipulate the odds of ending up in the egg rather than the polar body will have a transmission advantage, and will increase in frequency in a population. Segregation distortion can happen in several ways. When this process occurs during meiosis it is referred to as . Many forms of segregation distortion occur in male gamete formation, where there is differential

neg: Penicillium AIDS-associated pathogen, was also previously assumed to reproduce exclusively by asexual means. This assumption was largely based on the highly clonal population structure of this species. However, recent work has revealed that the genes required for meiosis are present in "P. marneffei". This and other evidence indicated that mating and genetic recombination does occur in this species. It was concluded that "P. marneffei" is sexually reproducing, but recombination is most likely to occur across spatially and genetically limited distances in natural populations resulting in a highly clonal population structure. These findings with "Penicillium" species are consistent with accumulating evidence from

neg: Parthenogenesis a human parthenogenetic stem cell line. Apomixis can apparently occur in "Phytophthora", an oomycete. Oospores from an experimental cross were germinated, and some of the progeny were genetically identical to one or other parent, implying that meiosis did not occur and the oospores developed by parthenogenesis. A form of asexual reproduction related to parthenogenesis is gynogenesis. Here, offspring are produced by the same mechanism as in parthenogenesis, but with the requirement that the egg merely be stimulated by the "presence" of sperm in order to develop. However, the sperm cell does not contribute any genetic material to the offspring. Since

neg: Lesion Lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. "Lesion" is derived from the Latin "laesio" "injury". Lesions may occur in plants as well as animals. There is no designated classification or naming convention for lesions. Because the definition of a lesion is so broad, the varieties of lesions are virtually endless. Although most frequently found in the mouth, on the skin, and in the brain, or anywhere where a tumor may occur, lesions can occur anywhere in the body that comprises soft tissue or osseous matter. Generally,

neg: Meiosis cellular reproduction, or during mitosis. Most monosomic and trisomic human embryos are not viable, but some aneuploidies can be tolerated, such as trisomy for the smallest chromosome, chromosome 21. Phenotypes of these aneuploidies range from severe developmental disorders to asymptomatic. Medical conditions include but are not limited to: The probability of nondisjunction in human oocytes increases with increasing maternal age, presumably due to loss of cohesin over time. Alongside with the variations of meiosis related to the moment when meiosis occur in life cycles, resulting in post-zygotic, pre-gametic and intermediate meiosis (see above), the number of nuclear divisions in meiosis

neg: Brachymeiosis form eight haploid nuclei in the ascospores. In 1895, the botanist R.A. Harper reported the observation of a second karyogamy event in the ascogonium prior to ascogeny. This would imply the creation of a tetraploid nucleus in the ascus, rather than a diploid one; in order to produce the observed haploid ascospores, a second meiotic reduction in chromosome count would then be necessary. The second reduction was hypothesized to occur during the second or third mitotic division in the ascus, even though chromosome reduction does not typically occur during mitosis. This supposed form of meiosis was termed “brachymeiosis” in 1908

neg: Damme Hills e. g. paddock). There are numerous paths for cyclists and hikers to enjoy the natural environment. The lake known as the "Damme Bergsee", roughly 25 ha in area, provides a refuge for rare animals and plants, which are described by means of a nature trail. Many endangered species of plant occur in this area: Of the hitherto 364 vascular plants, 68 species are on Lower Saxony's Red List of endangered types. One particularly notable group of animals are the reptiles, of which 4 species occur here: the grass snake, sand lizard, viviparous lizard and slowworm. From the bird world there

neg: Microbiota the host, parasitic, when disadvantageous to the host. Other authors define a situation as mutualistic where both benefit, and commensal, where the unaffected host benefits the symbiont. A nutrient exchange may be bidirectional or unidirectional, may be context dependent and may occur in diverse ways. Microbiota that are expected to be present, and that under normal circumstances do not cause disease, are deemed "normal flora" or "normal microbiota". The initial acquisition of microbiota in animals from mammalians to marine sponges is at birth, and may even occur through the germ cell line. In plants, the colonizing process can be initiated

neg: Ludwigia peploides months, the species will break up, dry out and decay but it has been seen that there are cases where it can survive. The reason these plants are scattered all over the globe is because "Ludwigia" can be generated during all seasons just from fragments of stems or rhizomes. They can be broken as easily by wind, water flow or animals. Lugwigia Peploides have the ability to double their biomass from their broken particles between 15 and 90 days. This also allows this species to continue to thrive in habitat and regions where sexual reproduction cannot occur. The "Ludwigia" occur

neg: Cay American English). A cay forms when ocean currents transport loose sediment across the surface of a reef to a depositional node, where the current slows or converges with another current, releasing its sediment load. Gradually, layers of deposited sediment build up on the reef surface. Such nodes occur in windward or leeward areas of reef where surfaces sometimes occur around an emergent outcrop of old reef or beach rock. The island resulting from sediment accumulation is made up almost entirely of biogenic sediment – the skeletal remains of plants and animals – from the surrounding reef ecosystems. If the accumulated

neg: Alpine plant plants, tissue desiccation is rare at high altitudes. If it does occur, it normally happens to plants growing on exposed sites, where wind stress is increased. Alpine plants avoid water loss by deep rooting and increased stomatal control. Plants at low elevation normally reach maximum stomatal opening in the morning while alpine plants reach maximum opening mid-day, when temperature is greatest. Alpine succulent plants often utilize CAM photosynthesis to avoid water loss. Because ultraviolet radiation tends to increase with elevation, it is often assumed to be a stress factor among alpine plants. In the past, there have been many attempts

neg: Balancer chromosome does occur during meiosis each chromatid ends up lacking some genes and carrying two copies of other genes. Recombination in inverted regions leads to dicentric or acentric chromosomes (chromosomes with two centromeres or no centromere). Progeny carrying chromosomes that are the products of recombination between balancer and normal chromosomes are not viable (they die). Dominant markers such as genes for green fluorescent protein or enzymes that make pigments allow researchers to easily recognize flies that carry the balancer chromosome. By suppressing reproductive fitness when carried homozygously a balancer chromosome ensures that the population it is carried in does not become

neg: Spindle apparatus centrosomes or asters that may be present at the spindle poles depending on the cell type. The spindle apparatus is vaguely ellipsoid in cross section and tapers at the ends. In the wide middle portion, known as the spindle midzone, antiparallel microtubules are bundled by kinesins. At the pointed ends, known as spindle poles, microtubules are nucleated by the centrosomes in most animal cells. "Acentrosomal" or "anastral" spindles lack centrosomes or asters at the spindle poles, respectively, and occur for example during female meiosis in most animals. In this instance, a Ran GTP gradient is the main regulator of spindle

neg: Homologous recombination Homologous recombination Homologous recombination is a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA. It is most widely used by cells to accurately repair harmful breaks that occur on both strands of DNA, known as double-strand breaks (DSB). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution. Homologous recombination is also

neg: Polyploidy in which a particular chromosome, or chromosome segment, is under- or overrepresented are said to be aneuploid (from the Greek words meaning "not", "good", and "fold"). Aneuploidy refers to a numerical change in part of the chromosome set, whereas polyploidy refers to a numerical change in the whole set of chromosomes. Polyploidy may occur due to abnormal cell division, either during mitosis, or commonly during metaphase I in meiosis. In addition, it can be induced in plants and cell cultures by some chemicals: the best known is colchicine, which can result in chromosome doubling, though its use may have other

neg: Spore megaspores or a microsporangium that produces microspores. In flowering plants, these sporangia occur within the carpel and anthers, respectively. Fungi commonly produce spores, as a result of sexual, or asexual, reproduction. Spores are usually haploid and grow into mature haploid individuals through mitotic division of cells (Urediniospores and Teliospores among rusts are dikaryotic). Dikaryotic cells result from the fusion of two haploid gamete cells. Among sporogenic dikaryotic cells, karyogamy (the fusion of the two haploid nuclei) occurs to produce a diploid cell. Diploid cells undergo meiosis to produce haploid spores. Spores can be classified in several ways: In fungi and

neg: Drosera anglica intermediary between that of "D. rotundifolia" and "D. linearis" and the two occur sympatrically in several locations, Wood conjectured that "D. anglica" likely originated from a hybrid between these two. All North American "Drosera" species produce sterile hybrids. The natural hybrid D. rotundifolia" × "D. linearis (conventionally but incorrectly referred to as "Drosera" ×"anglica"), is also sterile but is morphologically similar to the modern "D. anglica". Errors in meiosis during ovule and pollen production, however, can result in a chromosome doubling which can allow for viable seed to be produced. The resulting plants, known as amphiploids, would be fertile. Woods

neg: CITES 18) will be in Sri Lanka in 2019. The location of the next CoP is chosen at the close of each CoP by a secret ballot vote. The CITES Committees (Animals Committee, Plants Committee and Standing Committee) hold meetings during each year that does not have a CoP, while the Standing committee meets also in years with a CoP. The Committee meetings take place in Geneva, Switzerland (where the Secretariat of the CITES Convention is located), unless another country offers to host the meeting. The Animals and Plants Committees have sometimes held joint meetings. The previous joint meeting was held

neg: Physcomitrella patens originates a sporophyte composed of a foot, seta, and capsule, where thousands of haploid spores are produced by meiosis. "P. patens" is an excellent model in which to analyze repair of DNA damages in plants by the homologous recombination pathway. Failure to repair double-strand breaks and other DNA damages in somatic cells by homologous recombination can lead to cell dysfunction or death, and when failure occurs during meiosis, it can cause loss of gametes. The genome sequence of "P. patens" has revealed the presence of numerous genes that encode proteins necessary for repair of DNA damages by homologous recombination and

neg: Vertebrate thought to ordinarily occur between identical sister chromosomes and occasionally between homologous chromosomes. Thus little, if any, genetic variation is produced. Recombination between homeologous chromosomes occurs only rarely, if at all. Since production of genetic variation is weak, at best, it is unlikely to provide a benefit sufficient to account for the long-term maintenance of meiosis in these organisms. However, meiosis may have been maintained during evolution by the efficient recombinational repair of DNA damages that meiosis provides, an advantage that could be realized at each generation. The mangrove killifish ("Kryptolebias marmoratus") produces both eggs and sperm by meiosis and

neg: Fungus except Glomeromycota (genetic analysis suggests meiosis in Glomeromycota as well). It differs in many aspects from sexual reproduction in animals or plants. Differences also exist between fungal groups and can be used to discriminate species by morphological differences in sexual structures and reproductive strategies. Mating experiments between fungal isolates may identify species on the basis of biological species concepts. The major fungal groupings have initially been delineated based on the morphology of their sexual structures and spores; for example, the spore-containing structures, asci and basidia, can be used in the identification of ascomycetes and basidiomycetes, respectively. Fungi employ two mating

neg: Fungus insects to disperse their spores. Besides regular sexual reproduction with meiosis, certain fungi, such as those in the genera "Penicillium" and "Aspergillus", may exchange genetic material via parasexual processes, initiated by anastomosis between hyphae and plasmogamy of fungal cells. The frequency and relative importance of parasexual events is unclear and may be lower than other sexual processes. It is known to play a role in intraspecific hybridization and is likely required for hybridization between species, which has been associated with major events in fungal evolution. In contrast to plants and animals, the early fossil record of the fungi is meager.

neg: Genetic memory (biology) Genetic memory (biology) In biology, memory is present if the state of a biological system depends on its history in addition to present conditions. If this memory is recorded in the genetic material and stably inherited through cell division (mitosis or meiosis), it is genetic memory. "Somatic memory" is limited to the organism and not passed on to subsequent generations. However, its mechanism may involve mitotically stable genetic memory. The term applies for cellular memory, animals' memory, and plants' memory, as described in the following paragraphs. All cells in multicellular organisms are derived from a pluripotent zygote and contain the

neg: Fertilisation as in animals and plants. Meiosis results in a random segregation of the genes that each parent contributes. Each parent organism is usually identical save for a fraction of their genes; each gamete is therefore genetically unique. At fertilisation, parental chromosomes combine. In humans, (2²²)² = 17.6x10 chromosomally different zygotes are possible for the non-sex chromosomes, even assuming no chromosomal crossover. If crossover occurs once, then on average (4²²)² = 309x10 genetically different zygotes are possible for every couple, not considering that crossover events can take place at most points along each chromosome. The X and Y chromosomes undergo no

neg: Quantitative genetics lines with double arrow-heads are "correlation connections". Tracing various routes according to "path analysis rules" emulates the algebra of standardized partial regression. The path diagram to the left represents this analysis of sexual reproduction. Of its interesting elements, the important one in the selection context is "meiosis". That's where segregation and assortment occur—the processes that partially ameliorate the truncation of the phenotypic variance that arises from selection. The path coefficients b are the meiosis paths. Those labeled a are the fertilization paths. The correlation between gametes from the same parent (g) is the "meiotic correlation". That between parents within the

neg: Gene duplication unlikely to spread through populations. Whole genome duplication, or polyploidy, is a product of nondisjunction during meiosis which results in additional copies of the entire genome. Polyploidy is common in plants, but historically has also occurred in animals, with two rounds of whole genome duplication in the vertebrate lineage leading to humans. After whole genome duplications many sets of additional genes are eventually lost, returning to singleton state. However, retention of many genes, most notably Hox genes, has led to adaptive innovation. Polyploidy is also a well known source of speciation, as offspring, which have different numbers of chromosomes compared

neg: Nondisjunction form of cell division that involves ordered distribution of chromosomal material. Higher animals have three distinct forms of such cell divisions: Meiosis I and meiosis II are specialized forms of cell division occurring during generation of gametes (eggs and sperm) for sexual reproduction, mitosis is the form of cell division used by all other cells of the body. Ovulated eggs become arrested in metaphase II until fertilization triggers the second meiotic division. Similar to the segregation events of mitosis, the pairs of sister chromatids resulting from the separation of bivalents in meiosis I are further separated in anaphase of meiosis

neg: Genetic recombination to another, without the donating chromosome being changed. Gene conversion occurs at high frequency at the actual site of the recombination event during meiosis. It is a process by which a DNA sequence is copied from one DNA helix (which remains unchanged) to another DNA helix, whose sequence is altered. Gene conversion has often been studied in fungal crosses where the 4 products of individual meioses can be conveniently observed. Gene conversion events can be distinguished as deviations in an individual meiosis from the normal 2:2 segregation pattern (e.g. a 3:1 pattern). Recombination can occur between DNA sequences that contain

neg: Biological life cycle meiosis, also called somatic meiosis, which is a rare phenomenon. Vegetative meiosis can occur in haplodiplontic and also in diplontic life cycles. The gametophytes remain attached to and part of the sporophyte. Vegetative (non-reproductive) diploid cells undergo meiosis, generating vegetative haploid cells. These undergo many mitosis, and produces gametes. A different phenomenon, called vegetative diploidization, a type of apomixis, occurs in some brown algae (e.g., "Elachista stellaris"). Cells in a haploid part of the plant spontaneously duplicate their chromosomes to produce diploid tissue. The primitive type of life cycle probably had haploid individuals with asexual reproduction. Bacteria and archaea exhibit

neg: Regress argument no one ever seriously doubts. "Common sense" here does not mean old adages like "Chicken soup is good for colds" but statements about the background in which our experiences occur. Examples would be "Human beings typically have two eyes, two ears, two hands, two feet", or "The world has a ground and a sky" or "Plants and animals come in a wide variety of sizes and colors" or "I am conscious and alive right now". These are all the absolutely most obvious sorts of claims that one could possibly make; and, said Reid and Moore, these are the claims that

neg: Genetic engineering inserted gene. The presence of the gene does not guarantee it will be expressed at appropriate levels in the target tissue so methods that look for and measure the gene products (RNA and protein) are also used. These include northern hybridisation, quantitative RT-PCR, Western blot, immunofluorescence, ELISA and phenotypic analysis. The new genetic material can be inserted randomly within the host genome or targeted to a specific location. The technique of gene targeting uses homologous recombination to make desired changes to a specific endogenous gene. This tends to occur at a relatively low frequency in plants and animals and generally

neg: South India the southwest monsoon heads toward northeast India, picking up moisture from the Bay of Bengal. The Coramandel coast does not receive much rainfall from the southwest monsoon due to the shape of the land. Tamil Nadu and southeast Andhra Pradesh receive rains from the northeast monsoon. The northeast monsoon takes place from November to early March when the surface high-pressure system is strongest. The North Indian Ocean tropical cyclones occur throughout the year in the Bay of Bengal and the Arabian Sea, bringing devastating winds and heavy rainfall. There is a wide diversity of plants and animals in South India,

neg: Deoxyepinephrine Deoxyepinephrine Deoxyepinephrine, also known by the common names N-methyldopamine and epinine, is an organic compound and natural product that is structurally related to the important neurotransmitters dopamine and epinephrine. All three of these compounds also belong to the catecholamine family. The pharmacology of epinine largely resembles that of its "parent", dopamine. Epinine has been found in plants, insects and animals. It is also of significance as the active metabolic breakdown product of the prodrug ibopamine, which has been used to treat congestive heart failure. Epinine does not seem to occur widely, but it is present as a minor alkaloid in

neg: Wyre Forest redstart and long-eared owl, among many other woodland animals and plants. The small but colourful moth "Oecophora bractella" has one of its few English populations here, and does not seem to occur much further northwards. The forest's adders have been the subject of a notable study by Sylvia Sheldon. This historic extent of the Wyre Forest is debatable. Leaflets distributed in recent times have included Eymore Wood, in Kidderminster Foreign on the opposite bank of the River Severn, but that was merely a tract of woodland belonging to Worcester Cathedral. Another view is that once it stretched from Worcester to