Question 1

Which of the following best describes a sex-influenced trait?

Accepted Answer

A trait whose expression is conditioned or influenced by the sex of the individual, but the gene can be autosomal.

Question 2

A male moose has large antlers, while a female moose does not. Both sexes can carry the alleles for antlers. What type of inheritance does this represent?

Accepted Answer

Sex-limited inheritance

Question 3

A woman’s father has an X-linked recessive disorder, and her mother is homozygous for the wild-type allele. What is the woman’s genotype? (Use D for dominant and d for recessive allele.)

Accepted Answer

$$Dd$$

Question 4

If a woman with genotype $$Dd ($$where d is an X-linked recessive allele) has a son with a man who does not have the disorder, what is the probability that their son will have the disorder?

Accepted Answer

$$50\%$$

Question 5

Which of the following is a hallmark of X-linked recessive inheritance in a pedigree?

Accepted Answer

The trait can skip generations and is more common in males.

Question 6

A man with an X-linked dominant disorder has children with a woman who does not have the disorder. What is the expected outcome for their daughters?

Accepted Answer

All daughters will be affected.

Question 7

Which of the following statements is TRUE regarding Y-linked (holandric) inheritance?

Accepted Answer

Only males inherit Y-linked traits, and they are passed from father to all sons.

Question 8

A woman who is a carrier for an X-linked recessive disorder has a daughter with a man who does not have the disorder. What is the probability that the daughter will be a heterozygous carrier?

Accepted Answer

$$50\%$$

Question 9

Which of the following best explains why X-linked recessive disorders are more common in males?

Accepted Answer

Males are hemizygous for the X chromosome, so a single recessive allele will cause the disorder.

Question 10

A pedigree shows that only males are affected by a certain disorder, and the disorder is passed from unaffected mothers to affected sons. Which mode of inheritance is most likely?

Accepted Answer

X-linked recessive

Question 11

Which of the following is a key clue for identifying X-linked dominant inheritance in a pedigree?

Accepted Answer

Affected mothers pass the trait to half of their sons and half of their daughters.

Question 12

A woman with genotype $$Dd ($$where d is an X-linked recessive allele) has a daughter with a man who has genotype $$dY. $$What is the probability that their daughter will have the disorder?

Accepted Answer

$$50\%$$

Question 13

Which of the following is NOT a feature of sex-limited inheritance?

Accepted Answer

The trait is always inherited through the Y chromosome.

Question 14

In humans, red-green color blindness is X-linked recessive. If a color-blind woman has children with a man with normal vision, what is the expected outcome for their sons?

Accepted Answer

All sons will be color-blind.

Question 15

Which of the following best describes hemizygosity?

Accepted Answer

Having only one copy of a gene in a diploid cell, as in males for X-linked genes.

Question 16

A pedigree shows that all daughters of an affected father are affected, but none of his sons are. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Question 17

Which of the following is TRUE about sex linkage?

Accepted Answer

Sex linkage refers to genes located on sex chromosomes, affecting inheritance patterns.

Question 18

A woman who is heterozygous for an X-linked dominant disorder has children with a man who does not have the disorder. What is the probability that a child (regardless of sex) will have the disorder?

Accepted Answer

$$50\%$$

Question 19

Which of the following is a real-world example of a sex-influenced trait in humans?

Accepted Answer

Pattern baldness, which is dominant in males and recessive in females.

Question 20

A pedigree shows that an affected mother passes a disorder to half of her sons and half of her daughters, but an affected father passes it to all his daughters and none of his sons. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Sex and Heredity: Modes of Inheritance and Sex Dimorphism

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