Question 1

Which enzyme is responsible for cutting DNA at specific recognition sites, often resulting in fragments with overhangs on the 5' or 3' ends?

Accepted Answer

Restriction endonuclease

Question 2

During agarose gel electrophoresis, DNA fragments migrate towards which electrode, and why?

Accepted Answer

Positive anode, because DNA is negatively charged at physiological pH

Question 3

Which of the following best describes the difference between a plasmid and a cloning vector?

Accepted Answer

A plasmid is a naturally occurring circular DNA molecule, while a cloning vector is a plasmid or other DNA molecule engineered for gene transfer

Question 4

If you digest a double-stranded DNA molecule with EcoRI, which recognizes the sequence 5' GAATTC 3', what type of ends are produced?

Accepted Answer

Sticky ends with 5' overhangs

Question 5

During PCR, what is the purpose of the annealing step?

Accepted Answer

To allow primers to bind to complementary sequences on the template DNA

Question 6

Which of the following equations correctly represents the exponential amplification of DNA during PCR after $$n$$ cycles, starting with one template molecule?

Accepted Answer

$$2^n$$

Question 7

A researcher runs an agarose gel with five wells. She loads DNA samples of different sizes into each well. Which sample will migrate the farthest from the wells?

Accepted Answer

The smallest DNA molecule

Question 8

Which of the following is TRUE regarding the role of primers in PCR?

Accepted Answer

Primers are required to initiate DNA synthesis by providing a free 3' hydroxyl group

Question 9

In RT-PCR, which enzyme is responsible for synthesizing complementary DNA (cDNA) from an mRNA template?

Accepted Answer

Reverse transcriptase

Question 10

Which of the following best explains why DNA is negatively charged at physiological pH?

Accepted Answer

The phosphate groups in the DNA backbone lose protons, resulting in negative charges

Question 11

During the elongation step of PCR, which enzyme synthesizes the new DNA strand, and in which direction does it work?

Accepted Answer

DNA polymerase, synthesizing in the 5' to 3' direction

Question 12

Which of the following statements about cDNA is correct?

Accepted Answer

cDNA is synthesized from mRNA and contains only exons

Question 13

A scientist wants to detect the presence of a specific mRNA in a tissue sample. Which technique should she use?

Accepted Answer

In situ hybridization

Question 14

Which of the following is a clinical application of RT-PCR?

Accepted Answer

Detecting viral RNA in patient samples

Question 15

During PCR, what would happen if the annealing temperature is set too high?

Accepted Answer

Primers may not bind efficiently, resulting in little or no amplification

Question 16

Which of the following best describes the difference between DNA replication in cells and PCR?

Accepted Answer

DNA replication uses helicase to separate strands, while PCR uses heat

Question 17

Which of the following is required for both in situ hybridization and RT-PCR?

Accepted Answer

A nucleic acid probe that is complementary to the target sequence

Question 18

In a standard PCR reaction, which cycle first produces DNA fragments that are the exact length of the target sequence?

Accepted Answer

Third cycle

Question 19

Which of the following statements about restriction enzymes is FALSE?

Accepted Answer

They always produce blunt ends

Question 20

Which step in PCR involves the synthesis of new DNA strands by extending from the primers?

Accepted Answer

Elongation

Molecular Biology Techniques: DNA Cloning, Gel Electrophoresis, PCR, and RT-PCR

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