Male-biased mutation, sex linkage, and the rate of adaptive evolution

Mark Kirkpatrick1, David W Hall

  • 1Section of Integrative Biology, University Station C-0930, University of Texas, Austin, Texas 78712, USA. kirkp@mail.utexas.edu

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Overview
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X-linked Traits

In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.
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The Y Chromosome Determines Maleness

The Y chromosome is a sex chromosome found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human males have one X chromosome and one Y chromosome. In these organisms, the presence or absence of the Y chromosome determines the development of male traits.
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