Bio 180 Exam 3 Practice Questions and Answers (BYUI)|Accurate|Verified 2026

Bio 180 Exam 3 Practice Questions and
Answers (BYUI)


Question 1
Which of the following best describes the role of the ribosome in protein synthesis?

A. It stores genetic information
B. It catalyzes peptide bond formation
C. It transports amino acids into the nucleus
D. It modifies proteins in the Golgi apparatus

Rationale: Ribosomes are the site of translation, where mRNA is read and amino acids
are linked by peptide bonds to form polypeptides. They do not store genetic information
(DNA does), nor transport amino acids into the nucleus, nor function in protein
modification (Golgi does).

Question 2
During meiosis, crossing over occurs in which stage?

A. Prophase I
B. Metaphase I
C. Anaphase II
D. Telophase I

Rationale: Crossing over (exchange of genetic material between homologous
chromosomes) occurs during Prophase I, specifically in the pachytene stage, increasing
genetic diversity.

Question 3
Which of the following is a key difference between mitosis and meiosis?

A. Mitosis produces gametes, meiosis produces somatic cells
B. Mitosis results in diploid cells, meiosis results in haploid cells
C. Mitosis involves crossing over, meiosis does not
D. Mitosis occurs only in reproductive cells

Rationale: Mitosis produces genetically identical diploid cells, while meiosis reduces
chromosome number by half, producing haploid gametes. Crossing over is unique to
meiosis, not mitosis.

Question 4
Which enzyme is responsible for relieving supercoiling during DNA replication?

,A. DNA polymerase
B. Helicase
C. Topoisomerase
D. Ligase

Rationale: Topoisomerase prevents overwinding of DNA ahead of the replication fork.
Helicase unwinds DNA, polymerase synthesizes DNA, and ligase seals nicks.

Question 5
In population genetics, what does Hardy-Weinberg equilibrium assume?

A. Random mating and no evolution
B. Natural selection and genetic drift
C. Migration and mutation
D. Non-random mating and selection

Rationale: Hardy-Weinberg equilibrium assumes random mating, no mutation, no
migration, no selection, and large population size. Any violation leads to evolution.

Question 6
Which organelle is primarily responsible for ATP production in eukaryotic cells?
A. Nucleus
B. Mitochondria
C. Lysosome
D. Endoplasmic reticulum

Rationale: Mitochondria are the “powerhouses” of the cell, producing ATP via oxidative
phosphorylation.

Question 7
What is the main function of tRNA in translation?
A. Carrying genetic code
B. Bringing amino acids to ribosomes
C. Catalyzing peptide bonds
D. Editing mRNA

Rationale: tRNA molecules deliver specific amino acids to the ribosome, matching
codons with anticodons.

Question 8
Which phase of the cell cycle involves DNA replication?
A. G1
B. S phase
C. G2
D. M phase

, Rationale: DNA replication occurs during the S phase (synthesis phase).

Question 9
Which of the following is NOT a component of the endomembrane system?
A. Golgi apparatus
B. Rough ER
C. Lysosome
D. Mitochondria

Rationale: Mitochondria are independent of the endomembrane system.

Question 10
Which process increases genetic variation in gametes?
A. Binary fission
B. Crossing over
C. Cytokinesis
D. DNA replication

Rationale: Crossing over during meiosis I shuffles alleles, increasing variation.

Question 11
Which enzyme adds RNA primers during DNA replication?
A. Primase
B. Ligase
C. Helicase
D. Polymerase

Rationale: Primase synthesizes short RNA primers to initiate DNA synthesis.

Question 12
Which type of mutation does NOT change the amino acid sequence?
A. Missense
B. Nonsense
C. Silent
D. Frameshift

Rationale: Silent mutations alter the codon but still code for the same amino acid.

Question 13
Which structure separates homologous chromosomes during meiosis I?
A. Spindle fibers
B. Nuclear envelope
C. Centromere
D. Cytoplasm