110 likes | 258 Views
Sex-linked Traits. Autosomes vs. Sex chromosomes. X vs. Y chromosomes. See p. 213. Sex-linked. Genes that are located on the sex chromosomes X chromosome has more influence over phenotype
E N D
X vs. Y chromosomes • See p. 213
Sex-linked • Genes that are located on the sex chromosomes • X chromosome has more influence over phenotype • In males, there are no second copies of X-linked genes; if they have the rescessive allele, they will express it
Case Study • Chronic Granulomatous Disease (CGD) • The most common white blood cells -- neutrophils -- combat infections by producing germ-killing substances: hydrogen peroxide and bleach. People with CGD have genetic mutations that prevent the blood cells from making the proteins necessary for this process. As a result, infections that most of us easily fight are life-threatening to people with CGD.
Symbolizing sex-linked alleles • Use sex chromosomes instead of uppercase/lowercase letters • Use superscript to show whether they have a dominant or recessive gene
Practice Problem: A woman who is a carrier of CGD marries a man who has CGD. What are the genotypic and phentoypic chances for their offspring?
X chromosome inactivation • In females, 1 of the 2 X chromosomes is randomly “turned off”