Q: In Mendel’s classic pea plant experiments, what is the expected phenotypic ratio in the F2 generation when crossing two heterozygous (Pp) plants for flower color, where purple (P) is dominant to white (p)?

$$3 \text{ purple} : 1 \text{ white}$$

Q: In a dihybrid cross between two heterozygous pea plants ($$YyRr \times YyRr$$), where $$Y is $$yellow seed color (dominant), $$y is $$green, $$R is $$round (dominant), and $$r is $$wrinkled, what is the expected phenotypic ratio in the F2 generation?

$$9 \text{ yellow round} : 3 \text{ yellow wrinkled} : 3 \text{ green round} : 1 \text{ green wrinkled}$$

Q: In Labrador retrievers, coat color is determined by two genes: one for pigment color ($$B$$ for black, $$b$$ for brown) and one for pigment deposition ($$E$$ for color, $$e$$ for no color). What is the expected phenotypic ratio in the F2 generation from two $$BbEe$$ parents?

$$9 \text{ black} : 3 \text{ chocolate} : 4 \text{ yellow}$$

Q: A man with type A blood and a woman with type B blood have a child with type O blood. What are the genotypes of the parents?

$$I^A i$$ \text{ and } $$I^B i$$

Q: If a heterozygote for enzyme X (one effective, one ineffective allele) is crossed with another heterozygote, and the effective enzyme converts compound C (yellow) to D (red), what is the expected phenotypic ratio in the offspring?

$$3 \text{ red} : 1 \text{ yellow}$$

Question 1

In Mendel’s classic pea plant experiments, what is the expected phenotypic ratio in the F2 generation when crossing two heterozygous (Pp) plants for flower color, where purple (P) is dominant to white (p)?

Accepted Answer

$$3 	ext{ purple} : 1 	ext{ white}$$

Question 2

A testcross is performed between a pea plant with purple flowers of unknown genotype and a white-flowered plant (pp). If all offspring have purple flowers, what is the genotype of the purple-flowered parent?

Accepted Answer

$$PP$$

Question 3

Which of the following best explains why Mendel’s law of independent assortment does not always apply to all genes?

Accepted Answer

Some genes are located on the same chromosome and are inherited together.

Question 4

If a heterozygous pea plant for flower color ($$Pp) is $$crossed with a homozygous recessive plant ($$pp$$), what is the probability that an offspring will have white flowers?

Accepted Answer

$$\frac{1}{2}$$

Question 5

A couple has a child with Tay-Sachs disease, a recessive disorder. Neither parent nor their families have the disease. What is the probability that their next child will also have Tay-Sachs disease?

Accepted Answer

$$25\%$$

Question 6

In a dihybrid cross between two heterozygous pea plants ($$YyRr 	imes YyRr$$), where $$Y is $$yellow seed color (dominant), $$y is $$green, $$R is $$round (dominant), and $$r is $$wrinkled, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9 	ext{ yellow round} : 3 	ext{ yellow wrinkled} : 3 	ext{ green round} : 1 	ext{ green wrinkled}$$

Question 7

Which of the following is an example of codominance?

Accepted Answer

A person with type AB blood expresses both A and B antigens.

Question 8

A genetic counselor is working with a couple, both of whom have a sibling with a recessive genetic disorder. What is the probability that their child will have the disorder, assuming both are carriers?

Accepted Answer

$$\frac{1}{9}$$

Question 9

Which of the following best describes pleiotropy?

Accepted Answer

A single gene affects multiple phenotypic traits.

Question 10

In Labrador retrievers, coat color is determined by two genes: one for pigment color ($$B$$ for black, $$b$$ for brown) and one for pigment deposition ($$E$$ for color, $$e$$ for no color). What is the expected phenotypic ratio in the F2 generation from two $$BbEe$$ parents?

Accepted Answer

$$9 	ext{ black} : 3 	ext{ chocolate} : 4 	ext{ yellow}$$

Question 11

A man with type A blood and a woman with type B blood have a child with type O blood. What are the genotypes of the parents?

Accepted Answer

$$I^A i$$ 	ext{ and } $$I^B i$$

Question 12

Which of the following statements about dominant alleles is correct?

Accepted Answer

Dominant alleles are always expressed in the phenotype when present.

Question 13

If a heterozygote for enzyme X (one effective, one ineffective allele) is crossed with another heterozygote, and the effective enzyme converts compound C (yellow) to D (red), what is the expected phenotypic ratio in the offspring?

Accepted Answer

$$3 	ext{ red} : 1 	ext{ yellow}$$

Question 14

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes independently affect a single trait.

Question 15

A woman is heterozygous for the sickle-cell allele. What is her phenotype and what evolutionary advantage might she have?

Accepted Answer

She is healthy and less susceptible to malaria.

Question 16

If two dice are rolled, what is the probability that both will land on a six? (Use the multiplication rule.)

Accepted Answer

$$\frac{1}{36}$$

Question 17

Which of the following is an example of incomplete dominance?

Accepted Answer

A red flower crossed with a white flower produces pink flowers.

Question 18

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 19

Which of the following best describes a carrier for a recessive genetic disorder?

Accepted Answer

Heterozygous individual who does not express the disorder but can pass the allele to offspring.

Mendelian Genetics and Extensions: Principles, Patterns, and Applications

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