Unit 3 Problems to Know/Solve

Unit 3 – Problems to Know/Solve

Chapter 6 & Chapter 7

1. Eight-year-old Rhapsody has just learned that her younger brother Clyde is colorblind. Although she knows she has color vision because her cat, Juice, is clearly orange, and she reads that nearly all people with colorblindness are boys, she is concerned about her own sons one day. If she is a carrier for colorblindness, what is the minimum risk that a son of hers would be colorblind? XC or Xc = 50%

2. A healthy man and a healthy woman have a son with Lesch-Nyhan syndrome, an x- linked recessive trait. What are the chances that a daughter of this couple will inherit Lesch-Nyhan syndrome? XLY x XLXL or XLXl = XlXl = 0%

3. Cliff has colorblindness and icthyosis, which causes scaly skin. Both traits are x-linked recessive. What is the probability that he transmits both traits to his sons? 0% - He passes on the Y to his son

4. Determine the coefficient of relatedness between great grandparents and great grandchildren. ½ = 50% (parents) ½ x ½ = ¼ (grandparents) ¼ x ½ = 1/8 = 12.5% (great grandparents)

5. Jorge has hypertrichosis, an x-linked dominant trait. Jorge’s wife, Edwina, is a manifesting heterozygote for hypertrichosis. What are the odds of this couple having normal children? XH or Xh = 50%

6. 1/10,000 males are hemophiliacs, but only 1/100 million women have this sex-linked recessive trait. What are the odds of having a child with two hemophiliac parents (If this were possible)? 1/10,000 x 1/100,000,000 = 1/1,000,000,000,000