Non Mendelian Genetics: Sex-Linked Traits Lecture Notes

Karyotype: A photograph of a cell’s chromosomes arranged in ___________ according to size

Normal Karyotype: _______________ pairs of chromosomes

Sex-Linked Traits:

Those traits whose genes are found on the X chromosome but ________ on the Y chromosome

Examples of Sex-linked Traits:

Red-green colorblindness Male Pattern Baldness Hemophilia (Queen Victoria was a carrier) Duchene Muscular Dystrophy (fatal)

Sex-Linked Traits

Gene is attached to the X chromosome only, not found on the Y chromosome at all. Women have XX, men have XY chromosomes These disorders are more common in boys examples: red-green colorblindness

Sex-Linked Traits

In males, there is no second X chromosome to “_______________” a recessive gene. If _____________ get an X with the disorder, they have it. _______________ must inherit defective X’s from _______________ parents.

What is the number inside of each circle?___________, ____________, ____________,____________

Example of Sex-Linked Trait

H = Normal blood clotting h = Hemophilia

Example of Sex-Linked Trait

Normal male:_______________________ Male with Hemophilia:______________________ Normal female (not a carrier for hemophilia – homozygous):__________________ Normal female (carrier for hemophilia – heterozygous): _____________________ Female with Hemophilia: __________________________

Sample Problems

1. XHXh x XHY

Chances of: Punnett Square

a. hemophiliac child?

b. hemophiliac son?

c. hemophiliac daughter?

d. daughter who is carrier?

2. A woman who is a carrier for hemophilia marries a hemophiliac man.

Chances of: Punnett Square

a. hemophiliac child?

b. hemophiliac son?

c. hemophiliac daughter?

3. A normal man marries a Homozygous normal woman.

Chances of: Punnett Square

a. Will any of their kids be hemophiliacs?

4. A normal woman (whose father is a hemophiliac) marries a hemophiliac man.

What are their genotypes?