PCB 3063: Study Guide
PCB 3063
Spring 2012
Problem Set 1
ANSWERS
1. Determine the types of gametes produced by each of the following individuals: a. Aa 1/2 A, 1/2 a b. AaBb 1/4 AB, 1/4 Ab, 1/4 aB, 1/4 ab c. AABb 1/2 AB, 1/ Ab d. AaBBCc 1/4 ABC, 1/4 aBC, 1/4 ABc, 1/4 aBc
2. Use the Punnett square to determine the genotypes in the progeny of each of the following crosses: a. Dd x Dd b. AaBB x AaBB c. CcEE x CCEe Notice: in every case, each parent produces only two types of gametes.
[pic]
3. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A rough coated guinea pig is bred to a smooth one, giving eight rough and seven smooth progeny in the F1 generation. a. What are the genotypes of the parents and their offspring?
The recessive trait is observed in the progeny, so the rough-coated parent must be heterozygous. P: Rr (rough) x rr (smooth) F1: 1/2 Rr, 1/2 rr b. If one of the rough F1 animals is mated to its rough parent, what progeny would you expect?
This would be a monohybrid cross: Rr x Rr => 1/4 RR, 1/2 Rr, 1/4 rr.
4. In maize, a dominant allele A is necessary for seed color, as opposed to colorless (a). Another gene has a recessive allele w that results in waxy starch, as opposed to normal starch (W). The two genes segregate independently. What are the phenotypes and relative frequencies of offspring from each of the following crosses?
Notice: The question specifies phenotypic ratios. a. AaWw x AaWw
This is a dihybrid cross: 9/16 A_W_ (normal) 3/16 A_ww (waxy) 3/16 aaW_ (colorless) 1/16 aaww (waxy, colorless) b. AaWW x AaWW
This works like a monohybrid cross because both parents are homozygotic for WW. 3/4 A_WW (normal), 1/4 aaWW (colorless)
5. In humans, alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an autosomal allele (a) that is
Spring 2012
Problem Set 1
ANSWERS
1. Determine the types of gametes produced by each of the following individuals: a. Aa 1/2 A, 1/2 a b. AaBb 1/4 AB, 1/4 Ab, 1/4 aB, 1/4 ab c. AABb 1/2 AB, 1/ Ab d. AaBBCc 1/4 ABC, 1/4 aBC, 1/4 ABc, 1/4 aBc
2. Use the Punnett square to determine the genotypes in the progeny of each of the following crosses: a. Dd x Dd b. AaBB x AaBB c. CcEE x CCEe Notice: in every case, each parent produces only two types of gametes.
[pic]
3. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A rough coated guinea pig is bred to a smooth one, giving eight rough and seven smooth progeny in the F1 generation. a. What are the genotypes of the parents and their offspring?
The recessive trait is observed in the progeny, so the rough-coated parent must be heterozygous. P: Rr (rough) x rr (smooth) F1: 1/2 Rr, 1/2 rr b. If one of the rough F1 animals is mated to its rough parent, what progeny would you expect?
This would be a monohybrid cross: Rr x Rr => 1/4 RR, 1/2 Rr, 1/4 rr.
4. In maize, a dominant allele A is necessary for seed color, as opposed to colorless (a). Another gene has a recessive allele w that results in waxy starch, as opposed to normal starch (W). The two genes segregate independently. What are the phenotypes and relative frequencies of offspring from each of the following crosses?
Notice: The question specifies phenotypic ratios. a. AaWw x AaWw
This is a dihybrid cross: 9/16 A_W_ (normal) 3/16 A_ww (waxy) 3/16 aaW_ (colorless) 1/16 aaww (waxy, colorless) b. AaWW x AaWW
This works like a monohybrid cross because both parents are homozygotic for WW. 3/4 A_WW (normal), 1/4 aaWW (colorless)
5. In humans, alkaptonuria is a metabolic disorder in which affected persons produce black urine. Alkaptonuria results from an autosomal allele (a) that is