Q: Which equation would you use to calculate the probability of obtaining a double homozygous recessive genotype in a dihybrid cross?

$$P(aa\ bb) = P(aa) \times P(bb)$$

Q: Which equation represents the probability of obtaining a dominant phenotype in a dihybrid cross?

$$P(A-\ B-) = P(A-) \times P(B-)$$

Question 1

Which of the following best describes Mendel’s original experiments with pea plants?

Accepted Answer

He studied traits controlled by one gene, with two alleles showing complete dominance and 100% penetrance.

Question 2

In a dihybrid cross involving two genes that control the same trait, what phenotypic ratio is expected in the F2 generation if both genes are required for the wild-type phenotype?

Accepted Answer

9:7

Question 3

A cross between two true-breeding white-flowered pea plants yields all purple-flowered F1 offspring. What does this result indicate?

Accepted Answer

The two white strains have mutations in different genes that complement each other.

Question 4

Which equation would you use to calculate the probability of obtaining a double homozygous recessive genotype in a dihybrid cross?

Accepted Answer

$$P(aa\ bb) = P(aa) 	imes P(bb)$$

Question 5

In Labrador retrievers, coat color is determined by two genes: B (black/brown pigment) and E (expression of pigment). Which genotype results in a yellow coat?

Accepted Answer

$$B-\ ee$$

Question 6

What is the modified phenotypic ratio observed in the F2 generation of a dihybrid cross showing recessive epistasis?

Accepted Answer

9:3:4

Question 7

A complementation test is performed between two mutant strains with the same phenotype. The F1 offspring have the wild-type phenotype. What does this result mean?

Accepted Answer

The mutations are in different genes.

Question 8

Which of the following best explains duplicate dominant epistasis?

Accepted Answer

One dominant allele at either gene is sufficient for the dominant phenotype.

Question 9

In a cross of $$Aa\ Bb 	imes Aa\ Bb$$, what is the probability of obtaining an offspring with genotype $$aa\ bb$$?

Accepted Answer

$$\frac{1}{16}$$

Question 10

Which of the following is an example of conditional alleles affecting phenotype?

Accepted Answer

A rabbit with black fur at low temperatures and white fur at high temperatures.

Question 11

If two genes, C and P, are both required for purple flower color in peas, which genotype will result in white flowers?

Accepted Answer

$$C-\ pp$$

Question 12

Which of the following ratios is associated with duplicate recessive epistasis?

Accepted Answer

9:7

Question 13

A geneticist finds six mutant plants with white flowers. After performing pairwise complementation tests, three groups are found: two mutants fail to complement each other, three others fail to complement each other, and one complements all others. How many genes are involved?

Accepted Answer

Three genes

Question 14

Which of the following best describes the molecular explanation for multigenic traits controlling pigment production?

Accepted Answer

Both genes encode enzymes required for pigment biosynthesis; mutations in either gene disrupt pigment production.

Question 15

In a dihybrid cross, which ratio would you expect if a dominant allele at one locus masks the recessive phenotype at the other locus?

Accepted Answer

12:3:1

Question 16

Which of the following is NOT a modification to simple Mendelian inheritance?

Accepted Answer

Complete dominance with 100% penetrance

Question 17

A mouse with genotype $$B-\ ee$$ has what coat color, assuming B controls pigment and E controls expression?

Accepted Answer

Yellow

Question 18

Which of the following best describes the outcome of a cross between $$yy\ cc ($$cream) and $$Y^+y\ C^+c ($$red) pepper plants?

Accepted Answer

All F1 offspring will be red.

Question 19

Which equation represents the probability of obtaining a dominant phenotype in a dihybrid cross?

Accepted Answer

$$P(A-\ B-) = P(A-) 	imes P(B-)$$

Gene Interactions and Modifications to Mendelian Genetics

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