Dr. Mo Elkerdany
GENETICS..practice PROBLEMS
1. For each of the following GENOTYPES, give all possible GAMETES.
a. WW
b. WWSs
c. Tt
d. Ttgg
e. AaBb
f. LLFf
2. For each of the following, indicate whether it represents a GENOTYPE or a GAMETE.
a. D
b. Ll
c. Pw
d. LlGg
e. BbHH
3. If freckles are dominant to no freckles, and a man and a woman are both HETEROZYGOUS for freckles; what are the possible GENOTYPES and PHENOTYPES for their offspring? What is the probability that their first child will have freckles? What is the probability to have 2 children in a row with NO freckles?
4. Short fingers are DOMINANT over long fingers. A woman is HOMOZYGOUS dominant for short fingers. Will any of her children have long fingers?
5. Free earlobes are dominant over attached earlobes. Both you and your sister have attached earlobes, but your parents have free earlobes. Show the genotypes for all!!
6. Dimples are dominant over no dimples. If a man has dimples and a woman does NOT have dimples, and all of their children have dimples; show the genotypes for all!
7. If blue eyes are RECESSIVE to brown eyes; show the expected genotypes and phenotypes of the children of a marriage between a blue-eyed woman and a brown-eyed man who had a blue-eyed mother. What is the probability of this couple to have 2 blue-eyed daughters in a row!!
8. In humans, the gene for the ability to taste phenylthiocarbamide (PTC) is dominant over that for inability to taste PTC. The gene for brown eyes is dominant over that for blue eyes. WHAT [proportion of offspring of two parents, each is HETEROZYGOUS for both traits would be expected to be blue-eyed tasters of PTC? WHAT proportion of the offspring would be blue-eyed and non-tasters of PTC?
9. The gene for astigmatism is inherited as dominant. Two heterozygous for astigmatism marry. What is the probability that they will have 2 normal children in a row?
10. WHAT is the probability for a couple to have 2 boys in a row? And 3 boys in a row?!
11. Two brown-eyed parents have a blue-eyed child. What is the probability that their next child will be blue-eyed?
12. Albinism is autosomal recessive trait. A homozygous woman with normal pigmented skin married an albino man. What is the probability for this couple to have an albino child?
13. A man who has dimples and freckles marries a woman who does not have dimples or freckles. This couple produced a child that does NOT have dimples or freckles. Give the genotypes of all the individuals mentioned.
14. If this child (in question #13) marries someone who is heterozygous for both traits; what is the probability that they will have a child with the same GENOTYPE as its grandmother?!
15. Achondoplasia (dowarfism) is inherited as autosomal dominant trait. If a heterozygous man for the trait (dwarf) married a normal woman, what is their probability to have a normal height boy?
16. If two heterozygous (2 dwarfs) for the same trait (achondoplasia) married, what is their probability to have two normal children in a row?
17. From the following blood types; determine which baby belongs to which parents:
Mrs. Doe—blood type A Mr. Dow—blood type A
Mrs. Jones—blood type A Mr. Jones—blood type AB
Baby 1 -- blood type O Baby 2—blood type B
Doe’s baby is ______Jones’ baby is ______
18. Show that a child does NOT have to have the blood type of either parent by indicating that blood types might be possible when a person with blood type “A” reproduces with a person with blood type “B”.
19. A man with blood type “AB” has children with a woman with blood type “O”. What are the chances that a child they will conceive will have blood type “A”? Blood type “B”? Blood type “AB”? Or blood type “O”?
20. David is heterozygous for widow peak and dimples. Both widow’s peak and dimples are dominant traits. His wife is heterozygous for widow’s peak. She has NO dimples. What is the genotype of both?