Q: A population of beetles has two alleles for shell color: G (green, dominant) and g (brown, recessive). If 36% of the population is brown, what is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

Let $$q^2 = 0.36$, so q = 0.6$, p = 0.4$, and 2pq = 2$$ \times 0.4 \times 0.6 = 0.48$$ (48%).

Q: In a population, the frequency of allele A is 0.7 and allele a is 0.3. What is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

$$2pq = 2 \times 0.7 \times 0.3 = 0.42$$

Question 1

Which of the following best describes the difference between the blending theory of inheritance and Mendel’s particulate theory of inheritance?

Accepted Answer

Blending theory suggests that offspring are a mix of parental traits, while Mendel’s particulate theory states that traits are inherited as discrete units (genes) that do not blend.

Question 2

A woman with type AB blood and a man with type O blood have a child. Which blood types are possible for their child?

Accepted Answer

Type A or Type B

Question 3

In a population of 1000 individuals, 160 show the recessive phenotype for a trait controlled by a single gene with two alleles. Assuming Hardy-Weinberg equilibrium, what is the frequency of the dominant allele? (Let $$q^2$$ represent the frequency of the recessive phenotype.)

Accepted Answer

First, $$q^2$$ = \frac{160}{1000} = 0.16$$, so q$$ = \sqrt{0.16} = 0.4$$. Then p = 1 - q = 1 - 0.4 = 0.6$.

Question 4

Which of the following is an example of codominance?

Accepted Answer

A person with AB blood type expressing both A and B antigens equally.

Question 5

A man with genotype $$X^A Y$$ and a woman with genotype $$X^A X^a$$ for an X-linked recessive trait have a son. What is the probability that their son will express the recessive phenotype?

Accepted Answer

50%

Question 6

Which of the following is NOT a requirement for Hardy-Weinberg genetic equilibrium?

Accepted Answer

High mutation rate

Question 7

A population of beetles has two alleles for shell color: G (green, dominant) and g (brown, recessive). If 36% of the population is brown, what is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

Accepted Answer

Let $$q^2 = 0.36$, so q = 0.6$, p = 0.4$, and 2pq = 2$$ 	imes 0.4 	imes 0.6 = 0.48$$ (48%).

Question 8

Which of the following best describes the founder effect?

Accepted Answer

A small group colonizes a new area, leading to reduced genetic variation compared to the original population.

Question 9

In a pedigree, a trait appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 10

Which of the following scenarios illustrates directional selection?

Accepted Answer

A population of moths becomes darker over time as pollution increases, favoring dark-colored moths.

Question 11

Which of the following best explains why sexual reproduction increases genetic variation in a population?

Accepted Answer

It shuffles existing alleles through independent assortment, crossing over, and fertilization.

Question 12

A geneticist observes that a certain trait is only passed from mothers to all of their children, regardless of the children’s sex. What is the most likely mode of inheritance?

Accepted Answer

Mitochondrial inheritance

Question 13

If a population is not in Hardy-Weinberg equilibrium, which of the following could be a possible explanation?

Accepted Answer

There is non-random mating occurring in the population.

Question 14

A woman who is a carrier for an X-linked recessive disorder and a man who is unaffected have a daughter. What is the probability that the daughter will be affected by the disorder?

Accepted Answer

0%

Question 15

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

Accepted Answer

An individual with an abnormal number of chromosomes, such as Down syndrome (trisomy 21).

Question 16

In a population, the frequency of allele A is 0.7 and allele a is 0.3. What is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

Accepted Answer

$$2pq = 2 	imes 0.7 	imes 0.3 = 0.42$$

Question 17

Which of the following best describes stabilizing selection?

Accepted Answer

It favors individuals with average traits and selects against extremes.

Question 18

A pedigree shows that only males are affected by a certain trait, and the trait is never passed from father to son. What is the most likely mode of inheritance?

Accepted Answer

X-linked recessive

Question 19

Which of the following is a correct application of the law of independent assortment?

Accepted Answer

Alleles for different genes segregate independently during gamete formation if they are on different chromosomes.

Question 20

A population of mice has a gene with two alleles, B and b. If the frequency of the homozygous recessive genotype (bb) is 0.09, what is the frequency of the B allele?

Accepted Answer

$$q^2 = 0.09$, so q = 0.3$, p = 1 - 0.3 = 0.7$

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