Q: Given a population where the frequency of allele $$A$$ ($$p) is 0.7 $$and the frequency of allele $$a$$ ($$q) is 0.3$$, what is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium? Use the equation $$2pq.$$

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

Question 1

During DNA replication, which enzyme is responsible for unwinding the double helix, and what is the consequence if this enzyme is nonfunctional?

Accepted Answer

Helicase; DNA strands would remain coiled and replication could not proceed.

Question 2

Why does the lagging strand of DNA have to be synthesized in short fragments, and what are these fragments called?

Accepted Answer

Because DNA polymerase can only add nucleotides in the 5' to 3' direction; these are called Okazaki fragments.

Question 3

Which of the following correctly pairs the four nucleotide bases in DNA, and why is this pairing important for the structure of DNA?

Accepted Answer

Adenine with Thymine, Guanine with Cytosine; this pairing maintains a uniform width of the double helix due to purine-pyrimidine pairing.

Question 4

Which of the following best describes the function of mRNA in the process of gene expression?

Accepted Answer

It carries the genetic code from DNA in the nucleus to the ribosome for protein synthesis.

Question 5

During transcription, which base in RNA pairs with adenine in DNA, and what is the significance of this base?

Accepted Answer

Uracil; it replaces thymine in RNA, allowing RNA to be structurally distinct from DNA.

Question 6

A gene in a eukaryotic cell contains both introns and exons. What happens to these regions during mRNA processing?

Accepted Answer

Introns are removed and exons are spliced together to form the mature mRNA.

Question 7

Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

Accepted Answer

Small population size

Question 8

Given a population where the frequency of allele $$A$$ ($$p) is 0.7 $$and the frequency of allele $$a$$ ($$q) is 0.3$$, what is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium? Use the equation $$2pq.$$

Accepted Answer

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

Question 9

A population of birds is reduced to a few individuals after a hurricane. Over time, the genetic diversity of the population decreases. Which evolutionary mechanism is this an example of?

Accepted Answer

Bottleneck effect

Question 10

Which of the following best describes the difference between homologous and analogous structures?

Accepted Answer

Homologous structures have a common evolutionary origin, while analogous structures have similar function but evolved independently.

Question 11

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

Accepted Answer

Hybrid offspring are sterile and cannot reproduce.

Question 12

Which of the following scenarios best illustrates allopatric speciation?

Accepted Answer

A river divides a population of rodents, and over time, the two groups evolve into separate species.

Question 13

Which of the following is NOT a mechanism of evolution?

Accepted Answer

Mitosis

Question 14

Which of the following best defines a species according to the Biological Species Concept?

Accepted Answer

A group of populations whose members can interbreed and produce fertile offspring.

Question 15

Which of the following is evidence for natural selection, and why is antibiotic resistance in bacteria NOT considered artificial selection?

Accepted Answer

Antibiotic resistance evolves in response to environmental pressures, not human-directed breeding.

Question 16

Which of the following best describes the process of translation in protein synthesis?

Accepted Answer

The ribosome reads mRNA and assembles amino acids into a polypeptide chain.

Question 17

A hybrid zone forms between two closely related species of fish. Over time, hybrids have lower fitness than either parent species. What is the likely outcome?

Accepted Answer

Reinforcement of reproductive isolation between the two species.

Question 18

Which of the following equations represents the Hardy-Weinberg principle for genotype frequencies?

Accepted Answer

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

Question 19

Which of the following is an example of sexual selection?

Accepted Answer

Male peacocks with larger, more colorful tails are more likely to attract mates.

Question 20

Which of the following best describes punctuated equilibrium?

Accepted Answer

Species remain unchanged for long periods, interrupted by brief periods of rapid change.

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