Question 1

Which of the following best describes the main finding of the Meselson-Stahl experiment regarding DNA replication?

Accepted Answer

DNA replication is semiconservative, with each daughter molecule containing one parental and one new strand.

Question 2

A scientist is studying a bacterial strain with a mutation in the gene encoding DNA ligase. Which step of DNA replication would be most directly affected?

Accepted Answer

Joining of Okazaki fragments on the lagging strand.

Question 3

Which of the following statements about Chargaff's rules is correct?

Accepted Answer

The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Question 4

A mutation changes a codon from $$\mathrm{UAC} to$$ $$\mathrm{UAA}. $$What type of mutation is this, and what is its likely effect on the resulting protein?

Accepted Answer

Nonsense mutation; results in premature termination of translation.

Question 5

Which process is responsible for removing introns from a pre-mRNA transcript in eukaryotes?

Accepted Answer

RNA splicing

Question 6

In the context of the lac operon, what happens when both lactose and glucose are present in high concentrations in an E. coli cell?

Accepted Answer

The lac operon is only weakly expressed because glucose inhibits cAMP production, reducing CAP activation.

Question 7

Which of the following best explains why telomeres are important for eukaryotic chromosomes?

Accepted Answer

They prevent the loss of essential genetic information during DNA replication.

Question 8

A researcher uses PCR to amplify a segment of DNA. Which enzyme is essential for this process, and why?

Accepted Answer

Taq polymerase, because it synthesizes new DNA strands at high temperatures.

Question 9

Which of the following scenarios best illustrates post-translational modification?

Accepted Answer

A newly synthesized protein is phosphorylated to alter its activity.

Question 10

A patient is diagnosed with a genetic disorder caused by a single nucleotide substitution in a gene. Which molecular technique would be most appropriate to detect this mutation?

Accepted Answer

Southern blotting using a DNA probe specific for the mutated region.

Question 11

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 12

Which of the following is a key difference between prokaryotic and eukaryotic gene regulation?

Accepted Answer

Prokaryotes use operons for coordinated gene regulation, while eukaryotes typically regulate genes individually.

Question 13

A scientist wants to separate DNA fragments by size. Which technique should they use, and what is the principle behind it?

Accepted Answer

Gel electrophoresis; DNA fragments move through a gel matrix at rates inversely proportional to their size.

Question 14

Which of the following is true regarding the function of the trp operon in E. coli?

Accepted Answer

It is repressed when tryptophan is abundant, preventing unnecessary synthesis of tryptophan.

Question 15

Which of the following best describes the role of dideoxynucleotides in Sanger (dideoxy) DNA sequencing?

Accepted Answer

They terminate DNA strand elongation by lacking a 3' OH group.

Question 16

A eukaryotic gene is transcribed, but no functional protein is produced. Which regulatory mechanism could explain this observation?

Accepted Answer

The mRNA is degraded before translation due to post-transcriptional regulation.

Question 17

Which of the following best explains why DNA polymerase requires an RNA primer during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' OH group.

Question 18

Which of the following is a direct result of a frameshift mutation in a protein-coding gene?

Accepted Answer

The reading frame is altered, potentially changing every amino acid downstream of the mutation.

Question 19

Which of the following statements about genomes is correct?

Accepted Answer

A genome includes all the genetic material of an organism, including non-coding regions.

Question 20

A scientist is cloning a gene into a plasmid vector. Which of the following steps must occur for successful cloning?

Accepted Answer

The gene and plasmid must be cut with the same restriction enzyme to produce compatible ends.

General Biology: Molecular Genetics and Biotechnology (Chapters 16–21) – Study Notes

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