Question 1

Which of the following best describes the central dogma of molecular biology, and what enzymes are responsible for each step?

Accepted Answer

DNA $$\rightarrow$$ RNA $$\rightarrow$$ Protein; RNA polymerase for transcription, ribosome for translation

Question 2

Which of the following is an exception to the central dogma, and how does it alter the flow of genetic information?

Accepted Answer

Reverse transcription, where RNA is used as a template to synthesize DNA by reverse transcriptase

Question 3

Given the following DNA template strand: 3'-TACGGTACG-5', what is the corresponding mRNA sequence produced during transcription?

Accepted Answer

5'-AUGCCAUGC-3'

Question 4

A DNA sequence is mutated from 5'-ATG GAA TGA-3' to 5'-ATG GAG TGA-3'. What type of mutation is this, and what is the likely effect on the protein?

Accepted Answer

Missense mutation; a single amino acid is changed in the protein

Question 5

Why is the genetic code described as redundant, unambiguous, and nearly universal?

Accepted Answer

Because multiple codons can specify the same amino acid, each codon specifies only one amino acid, and the code is used by almost all organisms

Question 6

During eukaryotic mRNA processing, which of the following modifications occurs at the 3' end of the pre-mRNA, and what is its function?

Accepted Answer

Addition of a poly(A) tail; it stabilizes the mRNA and aids in export from the nucleus

Question 7

A tRNA molecule has the anticodon 5'-GAA-3'. Which mRNA codon will it recognize, and which amino acid will it carry?

Accepted Answer

3'-CUU-5' (mRNA codon 5'-UUC-3'); it will carry phenylalanine

Question 8

Which of the following best explains why there are fewer tRNAs and aminoacyl-tRNA synthetases (ARSs) than codons?

Accepted Answer

Because of wobble pairing, some tRNAs can recognize more than one codon

Question 9

A mutation in the lac operon causes the repressor protein to be unable to bind the operator. What is the expected outcome for lac operon expression in the presence and absence of lactose?

Accepted Answer

The operon will be expressed constitutively, regardless of lactose presence

Question 10

Which of the following best describes the difference between the lytic and lysogenic cycles of a bacteriophage?

Accepted Answer

In the lytic cycle, the virus immediately replicates and lyses the host cell; in the lysogenic cycle, the viral genome integrates into the host genome and can remain dormant

Question 11

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

Accepted Answer

Eukaryotes use chromatin remodeling to regulate transcription, while bacteria do not

Question 12

Which of the following best explains how alternative splicing increases protein diversity in eukaryotes?

Accepted Answer

By allowing different combinations of exons to be included in the final mRNA, producing multiple proteins from one gene

Question 13

In a PCR reaction, what is the purpose of the primers, and during which step do they anneal to the template DNA?

Accepted Answer

Primers provide a starting point for DNA synthesis; they anneal during the annealing step

Question 14

Which of the following best describes the role of ddNTPs in Sanger sequencing?

Accepted Answer

They terminate DNA synthesis at specific nucleotides, allowing the sequence to be determined

Question 15

A scientist uses the CRISPR-Cas9 system to inactivate a gene in human cells. Which components are required for this process?

Accepted Answer

Cas9 protein and a guide RNA complementary to the target gene

Question 16

Which of the following is evidence for genetic equivalence in animals?

Accepted Answer

The nucleus from a differentiated cell can direct development of an entire organism when transferred to an enucleated egg

Question 17

Which of the following best describes the difference between adult stem cells, embryonic stem cells, and induced pluripotent stem cells (iPSCs)?

Accepted Answer

Embryonic stem cells are pluripotent, adult stem cells are multipotent, and iPSCs are reprogrammed somatic cells that are pluripotent

Question 18

A patient is infected with an RNA virus that uses reverse transcriptase. Which enzyme(s) must the virus provide or encode to replicate its genome in a human cell?

Accepted Answer

Reverse transcriptase, because human cells do not have this enzyme

Question 19

Which of the following best explains how ubiquitin and the proteasome regulate protein levels in eukaryotic cells?

Accepted Answer

Ubiquitin tags proteins for degradation, and the proteasome degrades the tagged proteins

Molecular Biology, Gene Expression, and Biotechnology: Study Guide

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