1. Sex-Linked
Punnett Squares

2. Sex Determination X X X Y X X X X X Y X Y
Sex determined by genes found on the X and Y chromosome
Females: egg produced with an X chromosome
Males: ½ sperm cells contain X; and the other ½ contain Y
There is a 50/50 chance of child being a boy/girl

3. Sex-Linked Disorders
Defined: Inherited conditions found on X chromosome
Usually recessive
Females: XX chromosomes
XH XH = healthy
XH Xh = healthy carrier
Xh Xh = disease
Males: XY chromosomes
XHY = healthy
XhY = disease
Rare in women (back-up X chromosome)
Ex: Colorblindness, Hemophilia, Muscular dystrophy

4. Sample Colorblind Tests

5. Hemophilia and the Royal Family

6. Jen is a healthy carrier (XH Xh) of hemophilia and Adam has no history in his family (XH Y).
What is the probability of
getting:
Daughter with hemophilia? 0%
Carrier child?
25%
Child with hemophilia?
Two healthy children?
¾ x ¾ = 9/16 (56%)
Healthy girl
Healthy boy
Healthy girl (carrier)
Disease boy

7. Kelly is a healthy carrier of hemophilia, but Jim suffers from the disease.
What is the probability of getting a:
Healthy son?
25%
Healthy daughter?
Child with hemophilia?
50%
Carrier child?
Healthy girl (carrier)
Healthy boy
Disease girl
Disease boy

8. Sex linked recessive: Hemophilia

9. Sex linked recessive: Hemophilia

10. Kobe Kuiz
How are sex-linked disorders different from autosome disorders?
Why are sex-linked disorders more common in males?
Write the genotype of a heterozygous dominant female.
Write the genotype of a carrier female.
Examine Kelly and Jim’s Punnett square. What are the chances they would have three children, all of whom are healthy?