Sex-Linked Inheritance

Sex Determination Sex determined by genes found on the X and Y chromosome Females: egg produced with an X chromosome

Sex Determination 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

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 X X 50% Girl X Y X X X X 50% Boy X Y X Y

Sex-Linked Disorders XH XH XH Y XH Xh Xh Y Xh Xh 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) XH XH XH Y XH Xh Xh Y Xh Xh H = healthy h = disorder

Duchene Muscular Dystrophy 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) Examples of disorders: Duchene Muscular Dystrophy Hemophilia Colorblindness

Types of Colorblindness

Normal Deuteranopia (2.7%)

Normal Protanopia (0.59%)

Normal Tritanopia (0.016%)

Colorblind Test: Do you see a number inside the picture? 53

Colorblind Test: Do you see a number inside the picture? 12

Colorblind Test: Do you see a number inside the picture? 6

Colorblind Test: Do you see a number inside the picture? 74

Colorblind Test: Do you see a number inside the picture? 6

Hemophilia and the Royal Family

1 min: Discuss with your neighbor 1 min: Discuss with your neighbor. Jen is a healthy carrier (XH Xh) of hemophilia and Adam has no history in his family (XH Y). What is the probability of: a. Daughter with hemophilia? 0% b. Carrier child? 25% c. Child with hemophilia? d. Two healthy children? 9/16 (56%) Healthy girl Healthy boy Healthy girl (carrier) Hemophiliac boy 2010 2013 ¾ x ¾

Hemophilia is a sex linked disorder Hemophilia is a sex linked disorder. Kelly does not have hemophilia even though her mother did. Jim (Kelly’s husband) is a hemophiliac. Their first child Barry is healthy but their other child Rachel is a hemophiliac. Draw a Pedigree for this family and a Punnett square for Jim and Kelly. Xh Xh What is the probability of getting a: a. Healthy son? 25% b. Healthy daughter? c. Child with hemophilia? 50% d. Carrier child? Kelly’s mother Kelly Jim XH Xh Xh Y Barry Rachel Healthy girl (carrier) Healthy boy XH Y Xh Xh Hemophiliac girl Hemophiliac boy

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 XH Y XH Y Xh Y XH Y XH Y XH Y Males: XH Y or Xh Y XH Y Xh Y Xh Y Hint: Only 1 person is unknown.

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 Y Xh XH Y XH Xh XH Y Xh Y XH Y XH XH from mother from father Females: XHXH or XHXh XhXh XH Y XH Y Xh Y XH XH Y XH Xh Y Hint: Only 1 person is unknown.

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 XH Y XH Xh Xh Y XH Y Xh Y XH Y XH XH Xh Females: XHXH or XHXh XhXh XH Y XH Y XH XH Y Xh Y XH from mother from father Xh Y Hint: Only 1 person is unknown.

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 XH Y XH Xh XH Y Xh Y XH Y XH XH Xh Y Xh Females: XHXH or XHXh XhXh XH Y XH Y XH XH Y Xh Y Xh XH Xh Y from mother from father

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 XH Y XH Xh Xh XH XH Y Xh Y XH Y XH Xh XH Xh Females: XHXH or XHXh XhXh XH Y XH Y XH XH Y Xh Y Xh XH from father from mother Xh Y Hint: Only 1 person is unknown.

Sex linked recessive: Hemophilia Key XH = healthy Xh = hemophilia Sex linked recessive: Hemophilia 1 7 2 3 4 6 5 8 14 10 11 12 9 13 XH Y XH Xh XH XH Y Xh Y XH Y XH Xh XH Xh Females: XHXH or XHXh XhXh XH Y XH Y XH XH Y Xh Y Xh XH X? from father from mother Xh Y Hint: Only 1 person is unknown.

Quiz How are sex-linked disorders different from autosome disorders? Why are sex-linked disorders more common in males? Write the genotype of a heterozygous 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?