Question 1

A woman who is heterozygous for the X-linked recessive allele for hemophilia (normal phenotype) marries a man without hemophilia. What is the probability that their first child will be a son with hemophilia?

Accepted Answer

$$0.25$$

Question 2

A geneticist observes that two traits in fruit flies do not assort independently and are often inherited together. Which of the following best explains this observation?

Accepted Answer

The genes are linked and located close together on the same chromosome.

Question 3

A male honeybee develops from an unfertilized egg. Given that the diploid chromosome number in honeybees is $$32$$, what is the chromosome number in a male honeybee's somatic cells?

Accepted Answer

$$16$$

Question 4

A woman with normal vision whose father was color-blind marries a color-blind man. Red-green color blindness is X-linked recessive. What is the probability that their son will be color-blind?

Accepted Answer

$$0.50$$

Question 5

Which chromosomal abnormality results when a fragment of a chromosome breaks off and reattaches to the same chromosome in the reverse orientation?

Accepted Answer

Inversion

Question 6

A child is diagnosed with Down syndrome. How many chromosomes are present in each of their somatic cells?

Accepted Answer

$$47$$

Question 7

Which of the following best explains why Duchenne muscular dystrophy is almost never seen in girls?

Accepted Answer

A female must inherit two copies of the X-linked recessive allele to express the disorder.

Question 8

A Barr body is typically found in the nucleus of which type of human cell?

Accepted Answer

Somatic cells of a female only

Question 9

Which of the following is NOT an autosomal recessive disorder?

Accepted Answer

Fragile X syndrome

Question 10

A male calico cat is discovered, which is extremely rare. What is the most likely genetic explanation for this phenotype?

Accepted Answer

The male is XXY due to nondisjunction, allowing expression of both black and orange alleles.

Question 11

Which of the following best describes the inheritance pattern of mitochondrial DNA in humans?

Accepted Answer

Mitochondrial DNA is inherited exclusively from the mother.

Question 12

A geneticist observes that a particular allele has different effects depending on whether it was inherited from the mother or the father. This phenomenon is known as:

Accepted Answer

Genome imprinting

Question 13

A woman with patches of skin lacking sweat glands and other patches with normal sweat glands most likely exhibits which genetic phenomenon?

Accepted Answer

Chromosome inactivation

Question 14

Which of the following best describes aneuploidy?

Accepted Answer

$$2n + 1$$ 	ext{ or } 2n - 1$

Question 15

Which of the following human genetic disorders is sex-linked?

Accepted Answer

Hemophilia

Question 16

A man who carries an X-linked allele will pass it on to:

Accepted Answer

All of his daughters

Question 17

Which of the following best explains why individuals with an extra chromosome 21 (Down syndrome) are more numerous than those with an extra chromosome 3 or 16?

Accepted Answer

Extra copies of chromosomes 3 or 16 are likely fatal before birth.

Question 18

Which of the following is the correct chromosomal makeup for a human female?

Accepted Answer

XX

Question 19

Which of the following is a sex-influenced trait?

Accepted Answer

Male-pattern baldness

Question 20

Which of the following do all human males inherit from their mother?

Accepted Answer

Both mitochondrial DNA and the X chromosome

Chapter 15 Genetics and Chromosomal Inheritance – Guided Study

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