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The X-chromosome carries a larger number of genes in comparison to the Y-chromosome. In humans, X-chromosome inactivation enables males and females to have an equal expression of the genes on the X-chromosome since females have two X-chromosomes while males have a single X and a Y chromosome. X-chromosome inactivation is random in the somatic ...
Many insects of the order Hymenoptera instead have a haplo-diploid system, where the females are full diploids (with all chromosomes appearing in pairs) but males are haploid (having just one copy of all chromosomes). Some other insects have the X0 sex-determination system, where just the sex-determining chromosome varies in ploidy (XX in ...
Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. In the absence of a Y chromosome, the fetus will undergo female development. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. [5]
In this system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY). The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes , and are sometimes called allosomes.
This syndrome results from an extra copy of the X chromosome in each of a female's cells. Females with trisomy X have three X chromosomes, for a total of 47 chromosomes per cell. The average IQ of females with this syndrome is 90, while the average IQ of unaffected siblings is 100. [21] Their stature on average is taller than normal females.
The 23rd pair of chromosomes are called allosomes. These consist of two X chromosomes in females, and an X chromosome and a Y chromosome in males. Females therefore have 23 homologous chromosome pairs, while males have 22. The X and Y chromosomes have small regions of homology called pseudoautosomal regions.
According to the observation of embryonic cells of egg, chromosome number of the itch mite is either 17 or 18. While the cause for the disparate numbers is unknown, it may arise because of an XO sex determination mechanism, where males (2n=17) lack the sex chromosome and therefore have one less chromosome than the female (2n=18). [29] [29] 32 ...
In birds and some reptiles, by contrast, it is the female which is heterozygous and carries a Z and a W chromosome while the male carries two Z chromosomes. In mammals, females can have XXX or X. [30] [31] Mammalian females bear live young, with the exception of monotreme females, which lay eggs. [32]