Question 1

Which of the following best describes the role of DNA polymerase during DNA replication?

Accepted Answer

It adds nucleotides to the growing DNA strand in the 5' to 3' direction, using the template strand.

Question 2

In the classic Hershey-Chase experiment, what was the key evidence that DNA, and not protein, is the genetic material?

Accepted Answer

Radioactive phosphorus was found inside the bacterial cells, indicating DNA entered the cells.

Question 3

Which of the following statements about the structure of DNA is correct?

Accepted Answer

Adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds.

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 pre-mRNA in eukaryotic cells?

Accepted Answer

Splicing

Question 6

A researcher uses PCR to amplify a segment of DNA. Which of the following best describes the steps of PCR in the correct order?

Accepted Answer

Denaturation, annealing, extension

Question 7

Which of the following best explains how restriction enzymes are used in DNA cloning?

Accepted Answer

They cut DNA at specific sequences, allowing insertion of foreign DNA into plasmids.

Question 8

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

Accepted Answer

The operon is activated, and genes for lactose metabolism are transcribed.

Question 9

Which of the following best describes the function of eukaryotic enhancers?

Accepted Answer

They are DNA sequences that increase the rate of transcription when bound by specific proteins.

Question 10

A patient is diagnosed with a cancer caused by a mutation in a gene that normally inhibits cell division. This gene is most likely a:

Accepted Answer

Tumor suppressor gene

Question 11

Which of the following best explains why DNA fragments move at different rates during gel electrophoresis?

Accepted Answer

Smaller fragments move faster because they encounter less resistance in the gel matrix.

Question 12

Which of the following is an example of epistasis?

Accepted Answer

A gene for pigment production masks the effect of a gene for pigment color.

Question 13

Which of the following best describes the 'one gene – one polypeptide' hypothesis?

Accepted Answer

Each gene codes for a single polypeptide chain, which may be part of a protein.

Question 14

A DNA molecule has 30% adenine. According to Chargaff's rules, what percentage of guanine would you expect?

Accepted Answer

$$20\%$$

Question 15

Which of the following is a likely consequence of a frameshift mutation in a gene?

Accepted Answer

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

Question 16

Which of the following best describes the function of mRNA during translation?

Accepted Answer

It provides the template that determines the order of amino acids in the polypeptide.

Question 17

A scientist wants to amplify a specific gene from a small DNA sample. Which technique should they use, and what is the key enzyme involved?

Accepted Answer

PCR; Taq polymerase

Question 18

Which of the following is true about X-linked traits?

Accepted Answer

They are more likely to be expressed in males because males have only one X chromosome.

Question 19

Which of the following best describes the relationship between a codon and an amino acid?

Accepted Answer

Each codon is a sequence of three nucleotides that specifies a particular amino acid.

Question 20

Which of the following best explains why cancer can result from mutations in cell cycle control genes?

Accepted Answer

Mutations can lead to uncontrolled cell division by disrupting normal regulatory pathways.

Molecular Genetics and Biotechnology: Study Guide for Exam 4

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