Question 1

A mutation changes a single base in the coding region of a gene from GAA to GAG. Both codons code for glutamic acid. What type of mutation is this, and what is the likely effect on the protein produced?

Accepted Answer

Silent mutation; the protein will be unchanged because the amino acid sequence is the same.

Question 2

Which of the following best explains why DNA is more stable than RNA in the cell?

Accepted Answer

DNA has deoxyribose sugar, which lacks an oxygen atom, making the molecule less reactive and more stable.

Question 3

A researcher deletes the promoter region of a gene in a eukaryotic cell. What is the most immediate effect on gene expression?

Accepted Answer

The gene will not be transcribed because RNA polymerase cannot bind.

Question 4

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA acts as an adapter, matching mRNA codons with their corresponding amino acids.

Question 5

In eukaryotic cells, which process is responsible for removing introns from pre-mRNA?

Accepted Answer

Splicing by the spliceosome, which contains snRNA

Question 6

A cell is exposed to a chemical that prevents histone acetylation. What is the most likely effect on gene expression?

Accepted Answer

Genes will be less accessible, leading to decreased transcription.

Question 7

Which of the following events during meiosis is primarily responsible for Mendel’s law of segregation?

Accepted Answer

Separation of homologous chromosomes during anaphase I

Question 8

A DNA template strand has the sequence 3'-TAC GCT TTA GCG-5'. What is the corresponding mRNA sequence produced during transcription?

Accepted Answer

5'-AUG CGA AAU CGC-3'

Question 9

Which of the following best explains why alternative splicing increases protein diversity in humans?

Accepted Answer

It allows one gene to be transcribed into multiple types of mRNA, each coding for a different protein.

Question 10

A mutation causes a single nucleotide insertion in the coding region of a gene. What is the most likely consequence for the resulting protein?

Accepted Answer

A frameshift mutation; the reading frame will change, altering all downstream amino acids.

Question 11

Which of the following is a direct result of independent assortment during meiosis?

Accepted Answer

Different combinations of maternal and paternal chromosomes are distributed to gametes.

Question 12

In the lac operon of E. coli, what happens when lactose is present and glucose is low?

Accepted Answer

The operon is strongly activated; lactose removes the repressor and cAMP-CAP increases transcription.

Question 13

Which of the following best describes the flow of genetic information according to the central dogma of molecular biology?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$

Question 14

A cell has a mutation that prevents the addition of a poly-A tail to its mRNA. What is the most likely effect?

Accepted Answer

The mRNA will be rapidly degraded and less protein will be produced.

Question 15

Which of the following is a key difference between gene regulation in prokaryotes and eukaryotes?

Accepted Answer

Prokaryotes use operons for coordinated gene regulation, while eukaryotes regulate genes individually at multiple levels.

Question 16

A male with genotype XʰY (where ʰ is a recessive allele for colorblindness) and a female with genotype XᴴXʰ have a child. What is the probability that a son will be colorblind?

Accepted Answer

$$0.25$$

Question 17

Which of the following best explains why nondisjunction during meiosis can lead to genetic disorders such as Down syndrome?

Accepted Answer

It results in gametes with an abnormal number of chromosomes, such as trisomy 21.

Question 18

Which of the following regulatory mechanisms allows a single gene to produce multiple different proteins in eukaryotes?

Accepted Answer

Alternative splicing of pre-mRNA

Question 19

A scientist observes that a certain gene is highly methylated in liver cells but not in neurons. What is the most likely consequence of this methylation in liver cells?

Accepted Answer

The gene is less likely to be transcribed in liver cells.

Question 20

Which of the following best describes the role of microRNAs (miRNAs) in gene regulation?

Accepted Answer

They bind to mRNA and either degrade it or block its translation.

Genes, Gene Expression, and Genetic Inheritance: Ultra-Detailed Study Guide

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