Deck 3: Extensions to Mendels Laws

Question 1

If a phenotype is controlled by the genotypes at two different loci the interaction of these genes is called

A)epistasis.
B)epigenetics.
C)dominance.
D)codominance.
E)incomplete dominance.

Answer 1

epistasis.

Question 2

Which of the following phenotypic ratios show incomplete dominance?

A)2:1
B)3:1
C)1:2:1
D)1:1
E)4:1

Answer 2

1:2:1

Question 3

A number of interacting genes produce quantitative inheritance.The transmission of these genes can be seen in the phenotypical pattern of

A)discontinuous distribution of discrete phenotypes.
B)continuous variation in phenotypic expression.
C)strict dominance and recessiveness.
D)only discontinuous distribution of discrete phenotypes and continuous variation in phenotypic expression.

Answer 3

continuous variation in phenotypic expression.

Question 4

The gene that controls ABO blood type phenotype demonstrate which of the following inheritance patterns?

A)complete dominance.
B)recessiveness.
C)codominance.
D)complete dominance, recessiveness, and codominance
E)none of the choices is correct.

Question 5

If a gene is monomorphic in a population the most likely phenotypic ratio for the trait that would be obtained from a cross between two random individuals in the population would be

A)2:1
B)Cannot be predicted
C)1
D)3:1

Question 6

Which of the following is not a phenotypic description of allele interactions affecting the expression of traits?

A)incomplete dominance
B)codominance
C)polymorphic
D)multifactorial
E)pleiotrophic

Question 7

Predict the phenotypic ratio of the F₂ progeny of a parental cross between a homozygous black rat and an albino homozygous for cream.

A)1 albino : 2 black : 1 cream
B)9 black : 3 cream : 4 albino
C)9 black : 3 albino : 4 cream
D)12 black : 3 cream : 1 albino
E)12 black : 3 albino : 1 cream

Question 8

The phenotypic ratio 2:1 may indicate

A)complete dominance.
B)codominance.
C)epistasis.
D)recessive lethal.
E)codominance and epistasis only.

Question 9

A certain disease is caused by homozygosity of the g allele (G is the corresponding wild-type allele).However, the penetrance of the disease is 75%.Two individuals known to be heterozygotes have a child.What is the probability that the child exhibits the disease?

A)1/4
B)3/4
C)1/8
D)3/16
E)9/16
The child will exhibit the phenotype only if its genotype is gg.And if its genotype is gg, a 75% penetrance means that there is only a 75% chance that the gg genotype will cause the child to exhibit the phenotype.The chance that two heterozygotes (Gg * Gg) have a gg child is 1/4.Multiplying this probability by 75% gives 1/4 * 3/4 = 3/16

Question 10

The phenotypic ratio 9:3:4 may indicate

A)complete dominance.
B)codominance.
C)epistasis.
D)recessive lethal.
E)codominance and epistasis only.

Question 11

What would be an explanation for the phenomenon where a cross of a purebred, female, red eyed fruit fly with a purebred male, white eyed fly resulted in a phenotypic ratio that has a significantly greater number of red eyed flies than would be predicted by using Mendel's laws?

A)The red eye allele is dominant and sex linked.
B)The white eye allele is dominant and sex linked
C)The red eye allele is recessive and lethal
D)The white eye allele is recesive and lethal
E)male pattern baldness

Question 12

Predict the phenotypic ratio of the F₂ progeny of a cross between two colorless plants, one homozygous for A and the other homozygous for B.

A)3 colored : 1 colorless
B)9 colored : 7 colorless
C)9 colorless : 7 colored
D)15 colorless : 1 colored
E)15 colored : 1 colorless

Question 13

What can explain the phenomenon where the same genotype might give rise to different phenotypes?

A)pleiotropy
B)codominance
C)incomplete dominance
D)complete dominance
E)penetrance and expressivity

Question 14

Predict the genotypes and phenotypes of the F₁ progeny of a cross between a homozygous black rat and an albino homozygous for cream.

A)PPBB, black
B)PpBb, black
C)PpBb, albino
D)ppBb, albino

Question 15

Predict the genotypes and phenotypes of the F₁ progeny of a cross between two colorless plants, one homozygous for A and the other homozygous for B.

A)AAbb, colorless
B)aaBB, colorless
C)AaBb, colored
D)AaBb, colorless
E)aabb, colored

Question 16

Which of the following ratios show codominance?

A)2:1
B)3:1
C)1:2:1
D)1:1
E)4:1

Question 17

Which of the following ratios indicates a lethal gene?

A)2:1
B)3:1
C)1:2:1
D)1:1
E)4:1

Question 18

Which of the following ratios demonstrate gene interaction?

A)2:1
B)3:1
C)1:2:1
D)9:3:4
E)1:3

Question 19

The phenotypic ratio 9:7 may indicate

A)complete dominance.
B)codominance.
C)epistasis.
D)recessive lethal.
E)complementary gene action.

Question 20

Which ratio would indicate that a phenotype is controlled by multiple genes?

A)3:1
B)2:1
C)1:2:1
D)9:3:3:1.

Question 21

In some plants, a purple pigment is synthesized from a colorless precursor.In a cross between two parental plants, one purple and the other colorless, an F₁ generation was produced that was all purple.The F₂ produced from the F₁ had 775 purple, 200 red and 65 colorless plants.What mode of inheritance and phenotypic ratio do these results suggest?

A)Incomplete dominance, 1:2:1 phenotype ratio
B)Dominant epistasis, 12:3:1 phenotype ratio
C)Codominance, 1:2:1 phenotype ratio
D)Recessive epistasis, 9:3:4 phenotype ratio