Question 1

Which of the following best explains why the melting temperature ($$T_m) of $$DNA increases with higher GC content?

Accepted Answer

GC base pairs form three hydrogen bonds, making the DNA more stable and requiring more energy (higher temperature) to denature.

Question 2

A researcher uses a fluorescently labeled DNA probe to detect a specific gene sequence in a chromosome spread. Which technique is being used?

Accepted Answer

Fluorescent In Situ Hybridization (FISH)

Question 3

During PCR, why is it necessary to know the sequence of the DNA region to be amplified?

Accepted Answer

To design primers that are complementary to the flanking regions of the target sequence

Question 4

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

Accepted Answer

They terminate DNA synthesis by lacking a 3'-OH group, resulting in fragments of varying lengths.

Question 5

A DNA sample is subjected to increasing temperature and its absorbance at 260 nm is measured. The absorbance increases sharply at a certain temperature. What does this indicate?

Accepted Answer

The DNA strands are denaturing, separating into single strands.

Question 6

Which of the following statements about restriction enzymes is correct?

Accepted Answer

They recognize specific DNA sequences and cleave the DNA at or near these sites.

Question 7

In a restriction mapping experiment, digestion with EcoRI produces two fragments of 2.5 kb and 4.5 kb. Digestion with HaeIII produces fragments of 5.5 kb and 1.5 kb. Double digestion with both enzymes produces fragments of 2.5 kb, 3.0 kb, and 1.5 kb. Which restriction map is correct?

Accepted Answer

EcoRI site at 2.5 kb, HaeIII site at 5.5 kb (Map A)

Question 8

Which of the following is a key difference between Sanger sequencing and pyrosequencing?

Accepted Answer

Sanger sequencing uses chain-terminating ddNTPs, while pyrosequencing detects pyrophosphate release and light emission.

Question 9

A forensic scientist analyzes DNA from a crime scene using restriction digestion and Southern blotting. The resulting pattern matches the victim but not the suspect. What is this technique called?

Accepted Answer

DNA fingerprinting

Question 10

Which of the following best describes the process of DNA renaturation (reannealing)?

Accepted Answer

Single-stranded DNA molecules reassociate to form double-stranded DNA when temperature is lowered, allowing hydrogen bonds to reform.

Question 11

Which of the following is a necessary component for the polymerase chain reaction (PCR)?

Accepted Answer

Gene-specific primers

Question 12

Which of the following best explains why membranes enriched in unsaturated fatty acids have a lower transition temperature ($$T_m) $$than those enriched in saturated fatty acids?

Accepted Answer

Unsaturated fatty acids have kinks that prevent tight packing, increasing membrane fluidity and lowering $$T_m.$$

Question 13

Which of the following steps is NOT part of a typical PCR cycle?

Accepted Answer

Hybridization of a fluorescent probe to the DNA

Question 14

A scientist wants to compare a newly sequenced gene to all known genes in a database to find homologous sequences. Which tool should they use?

Accepted Answer

BLAST (Basic Local Alignment Search Tool)

Question 15

Which of the following is the correct equation for calculating the number of DNA molecules after $$n$$ cycles of PCR, starting from a single molecule?

Accepted Answer

$$N = 2^n$$

Question 16

Which of the following is a consequence of incorporating a dideoxynucleotide (ddNTP) during DNA synthesis in Sanger sequencing?

Accepted Answer

Chain termination due to the absence of a 3'-OH group

Question 17

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

Accepted Answer

It adds nucleotides to the 3'-OH end of a growing DNA strand using a template.

Question 18

In pyrosequencing, what is detected to determine which nucleotide was incorporated?

Accepted Answer

A flash of light produced by the reaction of pyrophosphate with luciferase

Question 19

Which of the following is a real-world application of DNA fingerprinting?

Accepted Answer

Identifying individuals in forensic investigations

Molecular Biology Techniques: DNA Hybridization, Fingerprinting, PCR, and Sequencing

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