Question 1

Which of the following best explains why feedback inhibition is beneficial to a cell's metabolic pathway?

Accepted Answer

It conserves cellular resources by inhibiting the activity of an early enzyme when the end product accumulates.

Question 2

A mutation causes the operator region of the lac operon to be permanently bound by the repressor protein. What is the most likely outcome for the cell when lactose is present?

Accepted Answer

The structural genes will not be transcribed, even in the presence of lactose.

Question 3

Which of the following events occurs during the S phase of interphase in the cell cycle?

Accepted Answer

DNA is replicated, resulting in sister chromatids.

Question 4

A researcher observes a tumor that has invaded neighboring tissues and entered the bloodstream. Which term best describes this tumor?

Accepted Answer

Malignant

Question 5

Which process during meiosis increases genetic variation by exchanging genetic material between homologous chromosomes?

Accepted Answer

Crossing over

Question 6

A woman who is a carrier for a sex-linked recessive disorder and a man who is unaffected have a son. What is the probability that their son will express the disorder?

Accepted Answer

$$0.50$$

Question 7

Which of the following best describes the role of tumor suppressor genes?

Accepted Answer

They repair damaged DNA or initiate apoptosis.

Question 8

In a dihybrid cross between two heterozygous pea plants (YyRr x YyRr), what is the probability of obtaining an offspring with the genotype yyrr?

Accepted Answer

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

Question 9

A population of 1,000 individuals has the following genotype frequencies: $$AA = 0.36$$, $$Aa = 0.48$$, $$aa = 0.16. Is $$this population in Hardy-Weinberg equilibrium?

Accepted Answer

Yes, because $$p^2 + 2pq$$ + $$q^2 = 1$ is satisfied.

Question 10

Which of the following is an example of disruptive selection?

Accepted Answer

Both small and large beak sizes are favored over medium beak sizes in a bird population.

Question 11

Which of the following statements about the lytic and lysogenic cycles of bacteriophages is correct?

Accepted Answer

In the lysogenic cycle, viral DNA integrates into the host genome and can be replicated with the host cell.

Question 12

Which of the following best describes the role of helper T-cells in the immune response?

Accepted Answer

They activate both B-cells and cytotoxic T-cells by releasing cytokines.

Question 13

Which of the following is a key difference between C4 and CAM plants in their adaptation to arid environments?

Accepted Answer

CAM plants open their stomata at night to minimize water loss, while C4 plants spatially separate carbon fixation.

Question 14

A population of beetles is reduced from 10,000 to 50 individuals due to a flood. Over time, the population recovers in size but shows reduced genetic diversity. Which evolutionary process best explains this scenario?

Accepted Answer

Bottleneck effect

Question 15

Which of the following is a postzygotic barrier to reproduction?

Accepted Answer

Hybrid sterility

Question 16

According to the endosymbiotic theory, which organelles are believed to have originated from free-living prokaryotes?

Accepted Answer

Mitochondria and chloroplasts

Question 17

Which of the following best describes the role of CRP (cAMP receptor protein) in the lac operon?

Accepted Answer

It acts as an activator, enhancing transcription when glucose is scarce.

Question 18

A scientist is constructing a phylogenetic tree and identifies a group that includes a common ancestor and all its descendants. What is this group called?

Accepted Answer

Monophyletic group

Question 19

Which of the following is a direct observation supporting natural selection?

Accepted Answer

The increase in frequency of antibiotic-resistant MRSA strains in hospitals.

Question 20

Which of the following best explains why sickle cell disease persists at relatively high frequencies in some human populations?

Accepted Answer

Heterozygotes have increased resistance to malaria, demonstrating heterozygote advantage.

AP Biology Semester 2 Final Exam Study Guide: Structured Study Notes

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