Question 1

Which of the following best explains why DNA strands are anti-parallel?

Accepted Answer

Hydrogen bonding between bases requires opposite orientation, and DNA polymerase only synthesizes DNA in the 5' → 3' direction.

Question 2

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 3

During DNA replication, a single nucleotide is deleted from a coding region. What is the most likely consequence?

Accepted Answer

The reading frame shifts, changing every codon after the mutation.

Question 4

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes contain the same genes but may have different alleles; sister chromatids are identical copies attached at the centromere.

Question 5

A patient has a mutation in a cell cycle checkpoint gene. Which of the following is a likely outcome?

Accepted Answer

The cell may proceed through the cycle with DNA errors, increasing cancer risk.

Question 6

Which stage of meiosis is responsible for separating homologous chromosomes?

Accepted Answer

Anaphase I

Question 7

If a DNA sequence is 5'-ATG AAA GGC TTT-3', and a single base is deleted after the first codon, what will happen to the protein product?

Accepted Answer

The reading frame will shift, altering all subsequent amino acids.

Question 8

Which of the following events increases genetic variation during sexual reproduction?

Accepted Answer

Crossing over during Prophase I of meiosis

Question 9

A cell with 2n chromosomes undergoes meiosis. What is the chromosome number in each resulting cell?

Accepted Answer

$$n$$

Question 10

Which of the following best describes the outcome of mitosis?

Accepted Answer

Two identical diploid cells

Question 11

During translation, which codon signals the start of protein synthesis?

Accepted Answer

AUG

Question 12

Which of the following is NOT a function of the centromere?

Accepted Answer

Initiating DNA replication

Question 13

A mutation changes a DNA codon but the resulting amino acid is unchanged. What type of mutation is this?

Accepted Answer

Silent mutation

Question 14

Which of the following best describes the process of crossing over?

Accepted Answer

Exchange of DNA between homologous chromosomes during Prophase I

Question 15

Which equation correctly represents the chromosome number after fertilization in humans?

Accepted Answer

$$1n + 1n = 2n$$

Question 16

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

Accepted Answer

Mitosis produces two identical diploid cells; meiosis produces four non-identical haploid cells.

Question 17

Which of the following is true about the directionality of DNA synthesis?

Accepted Answer

DNA is synthesized in the 5' → 3' direction.

Question 18

A cell undergoes a mutation that results in the addition of three nucleotides in a coding region. What is the most likely effect?

Accepted Answer

Addition of one amino acid; reading frame remains unchanged.

Question 19

Which of the following best describes the outcome of meiosis?

Accepted Answer

Four genetically different haploid cells

Question 20

Which step in translation is catalyzed by rRNA?

Accepted Answer

Formation of peptide bonds between amino acids

Genetics Study Notes: Mutations, Protein Translation, Mitosis, and Meiosis

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