Question 1

Which of the following best explains how meiosis contributes to genetic variation in sexually reproducing organisms?

Accepted Answer

By allowing for the independent assortment of homologous chromosomes and crossing over during prophase I.

Question 2

A human somatic cell contains 46 chromosomes. After DNA replication but before mitosis, how many chromatids are present in the cell?

Accepted Answer

$$92$$

Question 3

Which of the following scenarios best illustrates the concept of incomplete dominance?

Accepted Answer

A cross between a red-flowered and a white-flowered snapdragon produces all pink-flowered offspring.

Question 4

In a population of 1,000 individuals, the frequency of allele $$A is$$ $$0.7$$ and allele $$a is$$ $$0.3. $$Assuming Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes ($$Aa$$)?

Accepted Answer

$$0.42$$

Question 5

Which of the following is NOT an assumption of the Hardy-Weinberg equilibrium?

Accepted Answer

Natural selection is acting on the population.

Question 6

A woman who is a carrier for an X-linked recessive disorder and a man who does not have the disorder have a child. What is the probability that their son will have the disorder?

Accepted Answer

$$0.50$$

Question 7

Which of the following best describes genetic drift?

Accepted Answer

A change in allele frequencies due to random events, especially in small populations.

Question 8

Which of the following is an example of a postzygotic reproductive barrier?

Accepted Answer

Hybrid sterility

Question 9

If a diploid organism has a haploid number of $$n = 8$$, how many possible combinations of chromosomes can be produced in its gametes by independent assortment alone?

Accepted Answer

$$256$$

Question 10

Which of the following best explains why Down syndrome (trisomy 21) occurs?

Accepted Answer

Nondisjunction during meiosis leading to an extra chromosome 21.

Question 11

Which of the following is a real-world example of stabilizing selection?

Accepted Answer

Human birth weights being most common in the intermediate range, with very low and very high weights less frequent.

Question 12

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

They carry the same genes at the same loci, but may have different alleles.

Question 13

Which of the following mechanisms can result in sympatric speciation in plants?

Accepted Answer

Polyploidy resulting in reproductive isolation.

Question 14

A man with blood type AB and a woman with blood type O have children. What are the possible blood types of their children?

Accepted Answer

A and B only

Question 15

Which of the following is an example of frequency-dependent selection?

Accepted Answer

The fitness of a phenotype decreasing as it becomes more common in the population.

Question 16

Which of the following best describes the difference between a gene and an allele?

Accepted Answer

A gene is a segment of DNA that codes for a trait, while an allele is a variant form of that gene.

Question 17

Which of the following is a prezygotic barrier that can lead to reproductive isolation?

Accepted Answer

Gametic isolation

Question 18

A population of beetles has the following genotype frequencies: $$AA = 0.36$$, $$Aa = 0.48$$, $$aa = 0.16. $$What are the allele frequencies for $$A$$ and $$a$$?

Accepted Answer

$$A = 0.6$$, $$a = 0.4$$

Question 19

Which of the following best describes the evolutionary significance of sexual reproduction compared to asexual reproduction?

Accepted Answer

Sexual reproduction increases genetic variation, which can enhance adaptability in changing environments.

Question 20

Which of the following is an example of allopatric speciation?

Accepted Answer

A population of insects evolves into two species after being separated by a mountain range.

BIO 311D Exam 1 Study Guide: Genetics, Inheritance, Evolution, and Speciation

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