Q: Which of the following equations correctly represents the calculation for penetrance?

$$\text{Penetrance} = \frac{\text{# affected}}{\text{# with allele}} \times 100\%$$

Question 1

A cross between a red-flowered (RR) and a white-flowered (WW) snapdragon produces all pink flowers (RW). Which genetic phenomenon does this illustrate?

Accepted Answer

Incomplete dominance

Question 2

The ABO blood group system in humans is an example of which genetic principle?

Accepted Answer

Three alleles, codominance

Question 3

When one gene masks or suppresses the expression of another gene, this is called:

Accepted Answer

Epistasis

Question 4

A single gene that affects multiple, seemingly unrelated traits (such as sickle cell anemia affecting blood cells, immunity, and organ function) is an example of:

Accepted Answer

Pleiotropy

Question 5

Which of the following best describes Y-linked (holandric) inheritance?

Accepted Answer

Traits are passed from father to all sons

Question 6

A man with red-green color blindness (an X-linked recessive trait) and a woman with normal vision (not a carrier) have children. What is the probability that their son will be color blind?

Accepted Answer

$$0$$

Question 7

Which of the following statements about X-linked recessive inheritance is TRUE?

Accepted Answer

Females can be carriers without showing symptoms

Question 8

Pattern baldness in humans is an example of a sex-influenced trait because:

Accepted Answer

Its expression depends on the individual's sex and hormones

Question 9

A pedigree shows a trait that appears in every generation and affected individuals have at least one affected parent. This pattern is most consistent with:

Accepted Answer

Autosomal dominant inheritance

Question 10

Which of the following best describes the term 'penetrance'?

Accepted Answer

The percentage of individuals with a specific genotype who express the expected phenotype

Question 11

A woman who is a carrier for hemophilia (an X-linked recessive disorder) marries a man with normal blood clotting. What is the probability that their daughter will have hemophilia?

Accepted Answer

$$0.0$$

Question 12

Which of the following is a real-world example of a Y-linked trait?

Accepted Answer

Y-linked infertility

Question 13

If a gene is described as hemizygous in males, what does this mean?

Accepted Answer

Males have only one allele for the gene

Question 14

Which of the following equations correctly represents the calculation for penetrance?

Accepted Answer

$$	ext{Penetrance} = \frac{	ext{# affected}}{	ext{# with allele}} 	imes 100\%$$

Question 15

A man with normal vision (XNY) and a woman who is a carrier for red-green color blindness (XNXc) have a son. What is the probability that the son will be color blind?

Accepted Answer

$$0.5$$

Question 16

Which of the following is NOT a characteristic of X-linked dominant inheritance?

Accepted Answer

Affected fathers pass the trait to all sons

Question 17

A geneticist observes that a trait is dominant in males but recessive in females, even though the gene is autosomal. This is an example of:

Accepted Answer

Sex-influenced inheritance

Question 18

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

Accepted Answer

Males are hemizygous for the X chromosome

Question 19

A family pedigree shows a trait that is only passed from father to son and never appears in females. Which type of inheritance is most likely?

Accepted Answer

Y-linked

Question 20

Which of the following scenarios best illustrates gene-environment interaction?

Accepted Answer

A person with a genetic predisposition for polydactyly only develops extra digits if exposed to certain chemicals during development

Extensions of Mendelian Genetics: Sex-Linked Inheritance, Gene Interactions, and Genetic Background Effects

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