Genetics Exam with Multiple Choice
answers graded A+
1) A cross between a brown rat and a gray rat results in a large litter of pups, all of which are brown.
A cross between F1 siblings yields 3 brown pups for every 1 gray pup. Which is the dominant trait?
A) Gray
B) Brown and gray are co-dominant
C) Brown and gray show incomplete dominance
D) Brown
E) Coat color in rats shows variable expressivity - ANS✅✅D
2) Two parents, one with blood type A, and the other with type B, have a child who has O blood
type. What is the chance that their next three children will be type B?
A) 1/4
B) 1/8
C) 1/16
D) 1/32
E) 1/64 - ANS✅✅C
3) In cucumbers, an allele "Gl" for spiny cucumbers is dominant to an allele "gl" for glabrous
(spineless/hairless) cucumbers. A true breeding spiny plant is crossed to a true breeding glabrous
plant. F1 heterozygotes from this cross are then test-crossed to yield final offspring. What is the
expected phenotypic ratio of spiny to glabrous in the final generation?
A) 1:1
B) 1:2
C) 3:1
D) 1:2:1
E) 3:4 - ANS✅✅A
4) A mating of two organisms produces a 1:2:1 ratio of phenotypes in the progeny. The parental
genotypes, and the mode of inheritance are most likely:
A) Aa x aa, A is dominant to a
B) Aa x Aa, incomplete dominance or codominance
, C) AA x aa, incomplete dominance or codominance
D) Aa x Aa, X-linked, A is dominant to a
E) Aa x Aa, A is dominant to a - ANS✅✅
1) Select the smallest object.
A) A virus
B) A cell
C) A nucleotide
D) A cell nucleus
E) A chromosome - ANS✅✅
1) Shown below is a linear metabolic pathway in which a substrate metabolite W is converted into a
final product Z through a sequence of 3 steps catalyzed by different enzymes A, B and C. Each of the
enzymes is the product of a different gene.
ABCD
VWXYZ
You isolate a mutant that has higher than normal levels of metabolite W, but almost no metabolite
X. Which enzyme is most likely affected by the mutation?
A) A
B) B
C) C
D) W
E) X - ANS✅✅
1) The base composition of a DNA sample from C. elegans was determined. 20% of the bases were
found to be guanine. What is the percentage of adenine in the DNA?
A) 60%
B) 20%
C) 40%
D) 30%
E) 50% - ANS✅✅
answers graded A+
1) A cross between a brown rat and a gray rat results in a large litter of pups, all of which are brown.
A cross between F1 siblings yields 3 brown pups for every 1 gray pup. Which is the dominant trait?
A) Gray
B) Brown and gray are co-dominant
C) Brown and gray show incomplete dominance
D) Brown
E) Coat color in rats shows variable expressivity - ANS✅✅D
2) Two parents, one with blood type A, and the other with type B, have a child who has O blood
type. What is the chance that their next three children will be type B?
A) 1/4
B) 1/8
C) 1/16
D) 1/32
E) 1/64 - ANS✅✅C
3) In cucumbers, an allele "Gl" for spiny cucumbers is dominant to an allele "gl" for glabrous
(spineless/hairless) cucumbers. A true breeding spiny plant is crossed to a true breeding glabrous
plant. F1 heterozygotes from this cross are then test-crossed to yield final offspring. What is the
expected phenotypic ratio of spiny to glabrous in the final generation?
A) 1:1
B) 1:2
C) 3:1
D) 1:2:1
E) 3:4 - ANS✅✅A
4) A mating of two organisms produces a 1:2:1 ratio of phenotypes in the progeny. The parental
genotypes, and the mode of inheritance are most likely:
A) Aa x aa, A is dominant to a
B) Aa x Aa, incomplete dominance or codominance
, C) AA x aa, incomplete dominance or codominance
D) Aa x Aa, X-linked, A is dominant to a
E) Aa x Aa, A is dominant to a - ANS✅✅
1) Select the smallest object.
A) A virus
B) A cell
C) A nucleotide
D) A cell nucleus
E) A chromosome - ANS✅✅
1) Shown below is a linear metabolic pathway in which a substrate metabolite W is converted into a
final product Z through a sequence of 3 steps catalyzed by different enzymes A, B and C. Each of the
enzymes is the product of a different gene.
ABCD
VWXYZ
You isolate a mutant that has higher than normal levels of metabolite W, but almost no metabolite
X. Which enzyme is most likely affected by the mutation?
A) A
B) B
C) C
D) W
E) X - ANS✅✅
1) The base composition of a DNA sample from C. elegans was determined. 20% of the bases were
found to be guanine. What is the percentage of adenine in the DNA?
A) 60%
B) 20%
C) 40%
D) 30%
E) 50% - ANS✅✅
