This review introduces the differences in population history for sex chromosomes and autosomes, provides the expectations for genetic diversity across the genome under different evolutionary scenarios, and gives an introductory description for how deviations in these expectations are calculated and can be interpreted.
Humans have 22 pairs of autosomes and one pair of sex chromosomes the X and Y. Extreme selective sweeps independently targeted the X chromosomes of the great apes. Ao L et al. Evolution 61 4 — Then empirical observations of diversity on sex chromosomes across species are discussed, including how these fit, or deviate from, neutral expectations.
More About. Thus, sex chromosomes are of 2 types; X and Y. Evolution of sexual reproduction Anisogamy Isogamy Germ cell Meiosis Gametogenesis Spermatogenesis Oogenesis Gamete spermatozoon ovum Fertilization External fertilization Internal fertilization Sexual selection Plant reproduction Fungal reproduction Sexual reproduction in animals Sexual intercourse Copulation Human reproduction Lordosis behavior Pelvic thrust.
Humans have 22 pairs of autosomes and one pair of sex chromosomes the X and Y. The effects of genes carried only on the Y chromosome are, of course, expressed only in males.
Nat Rev Genet. Given that these are polygynous populations, the small effective numbers of males relative to females fig. Relative estimates of diversity uncorrected for mutation rate variation between the sex chromosomes and autosomes are plotted for male and female heterogametic systems under varying assumptions of mutation rate differences between males and females.
There are only two recognized species in Vampyrodes [ 6 ], whereas Platyrrhinus has at least 21 currently described species [ 54344 ]. The mechanism of sex determination in dioecious flowering plants. Sunderland MA: : Sinauer Associates; p. Li, Mutation rates differ among regions of the mammalian genome Nature :
Although evidence for selection has been inferred by comparing rates of polymorphism to divergence McDonald and Kreitman , this test can be biased by nonconstant effective population sizes Eyre-Walker and may be especially difficult to use to compare between the sex chromosomes and the autosomes.
X-autosome translocations: Cytogenetic characteristics and their consequences. Genet Res.