1. Sex-linked Traits

3. Autosomes vs. Sex chromosomes

4. X vs. Y chromosomes
See p. 213

5. 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

6. 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.

8. Symbolizing sex-linked alleles
Use sex chromosomes instead of uppercase/lowercase letters
Use superscript to show whether they have a dominant or recessive gene

9. 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?

10. X chromosome inactivation
In females, 1 of the 2 X chromosomes is randomly “turned off”

11. Quick Lab- sex-linked inheritance
p.202