Question 1

Which of the following best describes the role of a second messenger in cell signal transduction pathways?

Accepted Answer

It relays a signal from a membrane receptor to a target molecule inside the cell, often amplifying the signal.

Question 2

A researcher observes a cell with uncontrolled division and a failure to respond to normal regulatory signals. Which phase of the cell cycle is most likely disrupted in this cancerous cell?

Accepted Answer

G1 checkpoint

Question 3

During meiosis, crossing-over occurs at which stage, and what is its significance?

Accepted Answer

Prophase I; it increases genetic variation among gametes

Question 4

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

Accepted Answer

$$0.50$$

Question 5

Which of the following scenarios best illustrates the concept of genetic drift?

Accepted Answer

A population of beetles is reduced to a few individuals after a flood, and the surviving population has different allele frequencies than the original.

Question 6

Which equation represents the Hardy-Weinberg equilibrium for a gene with two alleles, $$p$$ and $$q$$?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 7

Which of the following best explains why linked genes do not assort independently?

Accepted Answer

They are located close together on the same chromosome and tend to be inherited together.

Question 8

A mutation changes a codon from UAC to UAA. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; results in a premature stop codon

Question 9

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

Eukaryotic genes contain introns that are removed during RNA processing.

Question 10

Which of the following best describes the function of an inducible operon, such as the lac operon in E. coli?

Accepted Answer

It is turned on in the presence of a specific substrate, allowing gene expression.

Question 11

Which of the following provides the strongest evidence for the theory of evolution by natural selection?

Accepted Answer

The fossil record showing transitional forms

Question 12

A population of 1,000 individuals has the following genotype frequencies: $$AA = 490$$, $$Aa = 420$$, $$aa = 90. $$What is the frequency of the $$a$$ allele?

Accepted Answer

$$0.30$$

Question 13

Which of the following is an example of epigenetic regulation of gene expression?

Accepted Answer

The addition of methyl groups to DNA, silencing gene expression

Question 14

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 15

Which of the following best describes the molecular clock hypothesis?

Accepted Answer

It estimates evolutionary time based on the rate of genetic mutations.

Question 16

A fruit fly geneticist observes that two genes are inherited together more often than expected by independent assortment. What is the most likely explanation?

Accepted Answer

The genes are linked and located close together on the same chromosome.

Question 17

Which of the following is a real-life example of frequency-dependent selection?

Accepted Answer

The fitness of a scale-eating fish depends on whether it bites the left or right side of its prey, and the rare form is favored.

Question 18

Which process is responsible for the packaging of DNA into chromosomes in eukaryotic cells?

Accepted Answer

Association of DNA with histone proteins to form nucleosomes

Question 19

Which type of selection favors individuals with intermediate phenotypes and reduces variation in a population?

Accepted Answer

Stabilizing selection

Question 20

A patient is diagnosed with a chromosomal disorder resulting from an extra copy of chromosome 21. What is the name of this condition?

Accepted Answer

Down syndrome

AP Biology Final Exam Study Guide: Cell Communication, Heredity, Gene Expression, and Evolution

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