Question 1

Consider a gene with four alleles A1, A2, A3, and A4. How many distinct heterozygous genotypes are possible?

Accepted Answer

A) 2 
B) 3 
C) 4 
D) 5 
E) 6

Question 2

If you crossed two heterozygous yellow-seed pea plants (genotypes Aa), the relative frequency of:

Accepted Answer

A) the a allele in each parent's gametes would be 1/2. 
B) the A allele in each parent's gametes would be 1/2. 
C) green-seed plants (genotype aa)would be 1/4. 
D) homozygous yellow-seed plants (genotype A
A) would be 1/4. 
E) All of these choices are correct.

Question 3

A recessive trait is expressed when the genotype is:

Accepted Answer

A) homozygous dominant or heterozygous. 
B) homozygous recessive or heterozygous. 
C) heterozygous only. 
D) homozygous dominant only. 
E) homozygous recessive only.

Question 4

Two genes, C and I, which undergo independent assortment, affect feather color in leghorn chickens. Each gene has two alleles, one of which is dominant for feather color. The gene product of the dominant allele C is necessary for color in the feathers; however, the gene product of the dominant allele I is an inhibitor of color production in the feathers, even when C is present. What ratio of white feathers : colored feathers is expected among the progeny of the cross Cc Ii × Cc Ii?

Accepted Answer

A) 9:7 
B) 10:6 
C) 12:4 
D) 13:3 
E) 15:1

Question 5

Which of the following statements are hallmarks of Mendel's Laws?

Accepted Answer

A) Alleles of a given gene always segregate with alleles of other genes located anywhere on the same chromosome. 
B) Two alleles of the same gene are normally inherited from the same parent. 
C) The alleles of a given gene will segregate as gametes are formed. 
D) All of these choices are correct.

Question 6

With independent assortment, the ratio of genotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

Accepted Answer

A) AA Bb 
B) Aa BB 
C) Aa Bb 
D) None of the answer options is correct.

Question 7

If the concept of blending inheritance were true, would variation increase or decrease over time?

Accepted Answer

A) It would increase. 
B) It would decrease. 
C) It would stay the same.

Question 8

Nondisjunction results in gametes that violate which of the following principles?

Accepted Answer

A) dominance 
B) segregation 
C) independent assortment 
D) epistasis

Question 9

Among the progeny of a heterozygous round (Aa) × homozygous wrinkled (aa) testcross, three seeds are chosen at random. What is the probability that two seeds are round and the other is wrinkled?

Accepted Answer

A) (1/2)3 
B) 2(1/2)3 
C) 3(1/2)3 
D) 4(1/2)3

Question 10

A _____ square is a useful diagram to show the results of an F1 × F1 cross.

Accepted Answer

A) Punnett 
B) Mendelian 
C) dominance 
D) genotype 
E) reciprocal

Question 11

In humans, ability to roll the tongue (R) is dominant to being unable to roll (r). Having freckles (F) is dominant to having no freckles (f). A man heterozygous for both traits marries a woman heterozygous for both traits. What is the probability that they will have a child with freckles?

Accepted Answer

A) 9/16 
B) 3/16 
C) 1/16 
D) 3/4 
E) 1/4

Question 12

In a reciprocal cross:

Accepted Answer

A) both parents are male. 
B) both parents are female. 
C) heterozygous genotypes are crossed with homozygous genotypes. 
D) the sexes are interchanged relative to the trait.

Question 13

In the F2 generation of a homozygous round (AA) × homozygous wrinkled (aa) cross in peas, two seeds are chosen at random. What is the probability that one is AA and the other aa?

Accepted Answer

A) (1/4)2 
B) (3/4)(1/4) 
C) 2(3/4)(1/4) 
D) (3/4)2

Question 14

_____ results in a given genotype not necessarily producing the same phenotype.

Accepted Answer

A) Incomplete penetrance 
B) Variable expressivity 
C) Incomplete dominance 
D) Principle of segregation

Question 15

Mendel used true-breeding strains of peas. Which true-breeding strain of peas would have been easier to produce: true-breeding peas with the trait caused by a dominant allele or a recessive allele?

Accepted Answer

A) dominant allele 
B) recessive allele 
C) Both strains would be equally easy to produce.

Question 16

The breeding example of White Leghorn chickens and White Wyandotte chickens, in which more than one gene controls pigment production, is an example of _____ interactions between genes.

Accepted Answer

A) epistatic 
B) incomplete dominance 
C) variable expressivity 
D) recessive 
E) dominant

Question 17

Consider a gene with four alleles A1, A2, A3, and A4. If the cross A1A2 × A3A4 yields two offspring, what is the probability that both of them have the same genotype?

Accepted Answer

A) 1/8 
B) 1/4 
C) 1/3 
D) 1/2 
E) 3/4

Question 18

Incomplete penetrance is synonymous with variable expressivity, because in both instances a trait may or may not be expressed.

Accepted Answer

A) True 
 B)False

Question 19

With independent assortment, the ratio of phenotypes in the F2 generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

Accepted Answer

A) recessive for both traits 
B) dominant for the A trait and recessive for the B trait 
C) dominant for one trait and recessive for the other 
D) dominant for both traits

Question 20

What is an allele?

Accepted Answer

A) one of several different forms of a gene 
B) the external appearance of an organism 
C) a spontaneous mutation 
D) a group of unrelated genes seen in true-breeding stock 
E) a circular strand of DNA capable of self-replication

Exam 16: Mendelian Inheritance

Consider a gene with four alleles A₁, A₂, A₃, and A₄. How many distinct heterozygous genotypes are possible?

If you crossed two heterozygous yellow-seed pea plants (genotypes Aa) , the relative frequency of:

A recessive trait is expressed when the genotype is:

Which of the following statements are hallmarks of Mendel's Laws?

With independent assortment, the ratio of genotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 1:2:1:2:4:2:1:2:1. To what genotype does the "4" in the ratio refer?

If the concept of blending inheritance were true, would variation increase or decrease over time?

Nondisjunction results in gametes that violate which of the following principles?

Among the progeny of a heterozygous round (Aa) × homozygous wrinkled (aa) testcross, three seeds are chosen at random. What is the probability that two seeds are round and the other is wrinkled?

A _____ square is a useful diagram to show the results of an F₁ × F₁ cross.

In humans, ability to roll the tongue (R) is dominant to being unable to roll (r) . Having freckles (F) is dominant to having no freckles (f) . A man heterozygous for both traits marries a woman heterozygous for both traits. What is the probability that they will have a child with freckles?

In a reciprocal cross:

In the F₂ generation of a homozygous round (AA) × homozygous wrinkled (aa) cross in peas, two seeds are chosen at random. What is the probability that one is AA and the other aa?

_____ results in a given genotype not necessarily producing the same phenotype.

Mendel used true-breeding strains of peas. Which true-breeding strain of peas would have been easier to produce: true-breeding peas with the trait caused by a dominant allele or a recessive allele?

The breeding example of White Leghorn chickens and White Wyandotte chickens, in which more than one gene controls pigment production, is an example of _____ interactions between genes.

Consider a gene with four alleles A₁, A₂, A₃, and A₄. If the cross A₁A₂ × A₃A₄ yields two offspring, what is the probability that both of them have the same genotype?

Incomplete penetrance is synonymous with variable expressivity, because in both instances a trait may or may not be expressed.

With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer?

What is an allele?