Question 1

A cross between a red-flowered and a white-flowered snapdragon produces all pink-flowered offspring. Which of the following best explains this result?

Accepted Answer

The alleles exhibit incomplete dominance, resulting in an intermediate phenotype.

Question 2

In the ABO blood group system, which genotype(s) will result in a person with blood type B?

Accepted Answer

Both $$I^B I^B$$ and $$I^B i$$

Question 3

A woman with blood type AB and a man with blood type O have a child. What is the probability that the child will have blood type A?

Accepted Answer

$$0.5$$

Question 4

A mutation in a gene results in a protein that is completely nonfunctional. This type of mutation is best described as:

Accepted Answer

A loss-of-function mutation resulting in a null allele

Question 5

In mice, the agouti allele ($$A) $$produces normal coat color, while the yellow allele ($$A^Y) is $$dominant for coat color but recessive lethal. What is the expected phenotypic ratio among the offspring of two yellow mice ($$A^Y A x$$ $$A^Y A$$)?

Accepted Answer

2 yellow : 1 agouti

Question 6

Which of the following best describes codominance?

Accepted Answer

Both alleles in a heterozygote are fully expressed, resulting in a distinct phenotype for each allele.

Question 7

A woman who is a carrier for red-green color blindness (an X-linked recessive trait) marries a man with normal vision. What is the probability that their son will be color blind?

Accepted Answer

$$0.5$$

Question 8

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both bone growth and heart function

Question 9

In the case of recessive epistasis, such as coat color in mice, what is the expected phenotypic ratio in the $$F_2$$ generation from a dihybrid cross ($$BbAa 	imes BbAa) if$$ $$bb is $$epistatic to $$A$$?

Accepted Answer

$$9:3:4$$

Question 10

A man with pattern baldness (autosomal, sex-influenced trait) and genotype $$Bb$$ marries a woman with genotype $$Bb. If$$ $$B is $$dominant in males and recessive in females, what is the probability that their daughter will be bald?

Accepted Answer

$$0$$

Question 11

Which of the following best explains the crisscross pattern of inheritance observed in X-linked recessive traits?

Accepted Answer

Affected mothers pass the trait to all sons, while carrier daughters can pass it to their sons.

Question 12

In summer squash, fruit color is determined by two genes. The presence of a dominant allele $$A$$ results in white fruit, regardless of the genotype at the second locus. If $$aa$$ and $$B-$$ genotypes produce yellow fruit, and $$aabb$$ produces green fruit, what is the expected phenotypic ratio from a cross between two $$AaBb$$ plants?

Accepted Answer

$$12:3:1$$

Question 13

Which of the following statements about multiple alleles is correct?

Accepted Answer

Multiple alleles refer to more than two alternative forms of a gene that can exist in a population.

Question 14

A woman with genotype $$I^A I^B ($$blood type AB) and a man with genotype $$I^B i ($$blood type B) have a child. What is the probability that the child will have blood type B?

Accepted Answer

$$0.5$$

Question 15

Which of the following is an example of sex-limited inheritance?

Accepted Answer

Hen and cock feathering in chickens, where only males can express cock feathering

Question 16

A man with Huntington disease (autosomal dominant, late onset) and genotype $$Hh$$ has children with a woman who is $$hh. $$What is the probability that a child will inherit the disease allele?

Accepted Answer

$$0.5$$

Question 17

Which of the following best describes epistasis?

Accepted Answer

The expression of one gene masks or modifies the effect of another gene at a different locus.

Question 18

In a dihybrid cross involving two genes with complementary gene interaction, both true-breeding white-flowered sweet peas are crossed and all $$F_1$$ offspring are purple. What is the expected $$F_2$$ phenotypic ratio for purple to white flowers?

Accepted Answer

$$9:7$$

Question 19

Which of the following statements about X-linked inheritance is correct?

Accepted Answer

Males are hemizygous for X-linked genes, so any allele present on the X chromosome will be expressed.

Question 20

A cross between two disc-shaped summer squash ($$AaBb x$$ $$AaBb) $$produces offspring with disc, sphere, and long fruit shapes. What is the expected phenotypic ratio for these three shapes?

Accepted Answer

$$9:6:1$$

Modification of Mendelian Ratios: Extensions and Exceptions to Classic Inheritance

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