Gnesh Kolker

Gnesh Kolker проживает в городе Lucknow, Индия. Родной город - miraj. Семейное положение Gnesh: не женат. Из открытых источников получены следующие сведения: информация о высшем и среднем образовании.

which have a ZW sex-determination system, the opposite is true: the W chromosome carries factors responsible for female development, and default development is male.[18] In this case ZZ individuals are male and ZW are female. The majority of butterflies and moths also have a ZW sex-determination system. In both XY and ZW sex determination systems the sex chromosome carrying the critical factors is often significantly smaller, carrying little more than the genes necessary for triggering the development of a given sex.[19] Many insects use a sex determination system based on the number of sex chromosomes. This is called XX/XO sex determination—the O indicates the absence of the sex chromosome. All other chromosomes in these organisms are diploid, but organisms may inherit one or two X chromosomes. In field crickets, for example, insects with a single X chromosome develop as male, while those with two develop as female.[20] In the nematode C. elegans most worms are self-fertilizing XX hermaphrodites, but occasionally abnormalities in chromosome inheritance regularly give rise to individuals with only one X chromosome—these XO individuals are fertile males (and half their offspring are male).[21] Other insects, including honey bees and ants, use a haplodiploid sex-determination system.[22] In this case diploid individuals are generally female, and haploid individuals (which develop from unfertilized eggs) are male. This sex-determination system results in highly biased sex ratios, as the sex of offspring is determined by fertilization rather than the assortment of chromosomes during meiosis.

: haploid fungi grow into contact with each other and then fuse their cells. In some of these cases the fusion is asymmetric, and the cell which donates only a nucleus (and not accompanying cellular material) could arguably be considered "male".[11] Some fungi, including baker's yeast, have mating types that create a duality similar to male and female roles. Yeast with the same mating type will not fuse with each other to form diploid cells, only with yeast carrying the other mating type.[12] Fungi produce mushrooms as part of their sexual reproduction. Within the mushroom diploid cells are formed, later dividing into haploid spores—the height of the mushroom aids the dispersal of these sexually produced offspring. Sex helps the spread of advantageous traits through recombination. The diagrams compare evolution of allele frequency in a sexual population (a) and an asexual population (b). The vertical axis shows frequency and the horizontal axis shows time. The alleles a/A and b/B occur at random. The advantageous combination AB arises rapidly with recombination (a), but must arise independently in (b).Evolution