Question 1

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

Accepted Answer

Males have only one X chromosome, so a single recessive allele will cause the disorder.

Question 2

A woman who is a carrier for hemophilia (an X-linked recessive disorder) and a man who does not have hemophilia have a son. What is the probability that their son will have hemophilia? Use the following notation: $$X^H = $$normal allele, $$X^h = $$hemophilia allele.

Accepted Answer

$$50\%$$

Question 3

Which of the following is an example of a sex-influenced trait rather than a sex-linked trait?

Accepted Answer

Pattern baldness

Question 4

Which chromosomal abnormality is most commonly associated with Down Syndrome?

Accepted Answer

Trisomy 21

Question 5

A pedigree shows a disease that skips generations and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 6

Which of the following best describes the genetic cause of cystic fibrosis?

Accepted Answer

A recessive mutation on chromosome 7 affecting chloride transport

Question 7

If a male with hemophilia (X-linked recessive) has children with a female who is not a carrier, what is the probability that their daughters will be carriers?

Accepted Answer

$$100\%$$

Question 8

Which of the following chromosomal abnormalities is most likely to result in a live birth?

Accepted Answer

Trisomy 21

Question 9

A genetic disorder is caused by a dominant allele. What is the probability that a child will inherit the disorder if one parent is heterozygous and the other is homozygous recessive?

Accepted Answer

$$50\%$$

Question 10

Which of the following best explains why females are less likely to express X-linked recessive disorders?

Accepted Answer

They have two X chromosomes, so a normal allele can mask the effect of a recessive allele.

Question 11

Which of the following is a result of nondisjunction during meiosis?

Accepted Answer

An egg or sperm with an abnormal number of chromosomes

Question 12

A child is born with Cri-du-chat syndrome. Which chromosomal event most likely caused this disorder?

Accepted Answer

A deletion on chromosome 5

Question 13

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

Accepted Answer

Y-linked traits are passed from father to all sons.

Question 14

A couple has a child with phenylketonuria (PKU), a recessive disorder. Neither parent has the disorder. What are the genotypes of the parents?

Accepted Answer

Both are heterozygous carriers

Question 15

Which of the following best describes a translocation event in chromosomes?

Accepted Answer

A piece of one chromosome breaks off and attaches to another chromosome

Question 16

A man with genotype $$Bb$$ for baldness (a sex-influenced trait) and a woman with genotype $$bb$$ have a son. If baldness is dominant in males and recessive in females, what is the probability their son will be bald?

Accepted Answer

$$50\%$$

Question 17

Which of the following is a characteristic of Huntington disease?

Accepted Answer

It is caused by a dominant allele and leads to progressive nerve degeneration.

Question 18

If a woman who is a carrier for an X-linked recessive disorder has children with a man who is affected by the disorder, what is the probability that their daughter will be affected?

Accepted Answer

$$50\%$$

Question 19

Which of the following best explains why dominant genetic disorders are less common in the population than recessive disorders?

Accepted Answer

Dominant disorders are more likely to be eliminated from the population because affected individuals often do not survive to reproduce.

Question 20

Which of the following statements about the X and Y chromosomes is correct?

Accepted Answer

The X chromosome contains many more genes than the Y chromosome.

Sex-Linked Inheritance and Chromosomal Abnormalities

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