Development <2 months gestation – embryo has rudimentary gonads
2 mos. SRY gene on Y chromosome active -> testes develop -> testosterone -> male If no SRY female default pathway ovaries
X-linked genes in humans Female genotypesMale genotypes X C X C X C X c X c X c X C Y X c Y Terms: homozygous, heterozygous, hemizygous Concept check: From whom do males obtain the Y chromosome? From whom do females obtain the X chromosomes? Why are X-linked disorders more prevalent in males?
Example: colorblindness 1/1O males Colorblindness is an X-linked trait. A man is colorblind. What % of his sons and daughters are expected to be colorblind. His wife does not carry the colorblind allele on either X chromosome.