Question 1

Which of the following best explains why phenylketonuria (PKU) is classified as a recessive genetic disorder?

Accepted Answer

Because only individuals with two defective PAH alleles show symptoms, as one functional allele is sufficient for normal enzyme activity.

Question 2

A child is born with oculocutaneous albinism (OCA). Which of the following genotypes must both parents have?

Accepted Answer

Both parents must be either carriers (Aa) or affected (aa) for the TYR gene.

Question 3

Which of the following foods should be strictly avoided by individuals with PKU, based on the dietary chart provided?

Accepted Answer

Eggs

Question 4

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

Accepted Answer

Autosomal recessive

Question 5

Which enzyme is deficient in individuals with oculocutaneous albinism (OCA), and what is the consequence?

Accepted Answer

Tyrosinase (TYR); inability to synthesize melanin from tyrosine

Question 6

A woman who is a carrier for hemophilia (XHXh) and a man who does not have hemophilia (XHY) have a child. What is the probability that their son will have hemophilia?

Accepted Answer

$$\frac{1}{2}$$

Question 7

Which of the following statements about polygenic traits is correct?

Accepted Answer

They are influenced by multiple genes and often show continuous variation in the population.

Question 8

In a cross between two individuals with the genotype AaBbCc (where each dominant allele contributes to darker fur), what is the expected proportion of offspring with the darkest fur (AABBCC)?

Accepted Answer

$$\frac{1}{64}$$

Question 9

Which of the following best describes the effect of gene linkage on inheritance patterns?

Accepted Answer

Linked genes tend to be inherited together because they are located close to each other on the same chromosome.

Question 10

A couple has a child with cystic fibrosis (CF), an autosomal recessive disorder. Neither parent has the disease. What is the probability that their next child will also have CF?

Accepted Answer

$$\frac{1}{4}$$

Question 11

Which of the following is a real-world reason for performing genetic testing on newborns?

Accepted Answer

To detect treatable genetic diseases early and prevent severe outcomes.

Question 12

Which of the following best explains why most traits are not purely genetic or purely environmental?

Accepted Answer

Most traits result from the interaction between multiple genes and environmental factors.

Question 13

A man with genotype XhY (hemophilia) and a woman with genotype XHXh (carrier) have a daughter. What is the probability that she will have hemophilia?

Accepted Answer

$$\frac{1}{4}$$

Question 14

Which of the following is an example of a monogenic trait?

Accepted Answer

Widow’s peak hairline

Question 15

Which of the following best describes the inheritance pattern of familial hypercholesterolemia (FH)?

Accepted Answer

Incompletely dominant

Question 16

If a woman with genotype XHXh (carrier for hemophilia) and a man with genotype XHY have two children, what is the probability that both will be sons with hemophilia?

Accepted Answer

$$\frac{1}{16}$$

Question 17

Which of the following statements about sickle cell anemia is correct?

Accepted Answer

It is caused by a recessive mutation in the HBB gene and leads to abnormal red blood cell shape.

Question 18

Which of the following best explains why individuals with PKU must avoid aspartame?

Accepted Answer

Aspartame contains phenylalanine, which cannot be metabolized by individuals with PKU.

Question 19

Which of the following is true regarding the SRY gene?

Accepted Answer

It is located on the Y chromosome and triggers male development.

Patterns of Inheritance: Monogenic and Polygenic Traits, Genetic Diseases, and Sex-Linked Inheritance

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