Question 1

Which of the following best explains why males are more likely than females to express X-linked recessive disorders such as color blindness?

Accepted Answer

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

Question 2

A pedigree chart shows a disorder appearing in every generation and affecting both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 3

Which chromosomal mutation involves a segment of a chromosome being reversed end to end?

Accepted Answer

Inversion

Question 4

Familial hypercholesterolemia is caused by a defective LDLR gene. If a child inherits one defective allele from a parent with the disorder and one normal allele from the other parent, what is the expected phenotype?

Accepted Answer

The child will have high cholesterol levels and show symptoms of the disorder.

Question 5

Which equation correctly represents the probability of a child inheriting an autosomal recessive disorder if both parents are heterozygous ($$Aa 	imes Aa$$)?

Accepted Answer

$$P = 1/4$$

Question 6

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?

Accepted Answer

$$P = 1/2$$

Question 7

Which chromosomal abnormality is associated with chronic myelogenous leukemia (CML) and involves a translocation between chromosomes 9 and 22?

Accepted Answer

Philadelphia chromosome

Question 8

If nondisjunction occurs during meiosis II in a female, what is the possible chromosomal composition of her gametes?

Accepted Answer

Some gametes will have $$n+1$$ chromosomes, some will have $$n-1$$, and some will be normal.

Question 9

Which of the following best describes polyploidy?

Accepted Answer

A condition where an organism has more than two complete sets of chromosomes.

Question 10

A couple, both carriers for sickle cell anemia ($$Ss$$), have a child. What is the probability that the child will be homozygous normal ($$SS$$)?

Accepted Answer

$$P = 1/4$$

Question 11

Which of the following is a key feature of genes that are linked on the same chromosome?

Accepted Answer

They tend to be inherited together unless crossing over occurs.

Question 12

Which syndrome results from the presence of only one X chromosome and no second sex chromosome (XO) in females?

Accepted Answer

Turner syndrome

Question 13

Which of the following is NOT a symptom of Huntington’s disease?

Accepted Answer

Excess cholesterol in blood

Question 14

Which process during meiosis is responsible for the segregation and independent assortment of alleles?

Accepted Answer

Separation of homologous chromosomes

Question 15

A child is born with Down syndrome. Which chromosomal abnormality is most likely responsible?

Accepted Answer

Trisomy 21

Question 16

Which of the following Punnett squares correctly predicts the offspring of two parents who are both heterozygous for hereditary deafness ($$Dd 	imes Dd$$)?

Accepted Answer

$$DD, Dd, Dd, dd$$

Question 17

Which of the following is a consequence of a chromosomal translocation?

Accepted Answer

A segment of a chromosome is moved to a non-homologous chromosome.

Question 18

If a female carrier for color blindness (X-linked recessive) mates with a normal male, what is the probability that their daughter will be color blind?

Accepted Answer

$$P = 1/4$$

Question 19

Which of the following best describes aneuploidy?

Accepted Answer

The presence of an abnormal number of chromosomes in a cell.

Question 20

Which of the following is a real-world example of a disorder caused by a dominant allele?

Accepted Answer

Huntington’s disease

Chromosomes and Human Genetics: Patterns of Inheritance and Chromosomal Mutations

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