Question 1

Which of the following best explains why Taq polymerase is essential for the Polymerase Chain Reaction (PCR)?

Accepted Answer

Taq polymerase is derived from a thermophilic bacterium, allowing it to withstand the high temperatures required for DNA denaturation in PCR.

Question 2

A researcher wants to amplify a specific DNA sequence from a small blood sample to detect a genetic mutation. Which technique should they use, and what is the key equation that describes the exponential amplification of DNA during this process?

Accepted Answer

They should use PCR; the amplification is described by $$N = N_0$ 	imes 2^n$$, where $$N is $$the final number of DNA molecules, $$N_0 is $$the initial number, and $$n is $$the number of cycles.

Question 3

What is the primary purpose of molecular cloning in biotechnology?

Accepted Answer

To create multiple copies of a specific DNA sequence and express it in a host organism.

Question 4

PUC19 is considered a great cloning vector for several reasons. Which of the following is NOT a feature that makes PUC19 advantageous?

Accepted Answer

It is naturally resistant to all known antibiotics, making selection unnecessary.

Question 5

EcoRI is commonly used in molecular biology. What is its function?

Accepted Answer

EcoRI is a restriction endonuclease that cuts DNA at a specific palindromic sequence.

Question 6

A scientist wants to produce human insulin in E. coli. Which of the following steps is NOT required in the process?

Accepted Answer

Directly injecting purified human insulin protein into E. coli cells.

Question 7

Which of the following best describes a reporter gene and identifies the gene whose product yields a green color?

Accepted Answer

A reporter gene is a gene that encodes a protein used to monitor gene expression; the green fluorescent protein (GFP) gene yields a green color.

Question 8

What is a major advantage of using genetically engineered bacteria to produce insulin compared to extracting insulin from animal pancreases?

Accepted Answer

Genetically engineered insulin can be produced in large quantities and is identical to human insulin, reducing allergic reactions.

Question 9

Which of the following best defines a transgenic plant?

Accepted Answer

A plant that contains a gene from another species introduced by genetic engineering.

Question 10

Recombinant bovine somatotropin (rBST) is used in agriculture. How is rBST produced and what is its primary use?

Accepted Answer

rBST is produced by genetically engineered bacteria expressing the bovine somatotropin gene and is used to increase milk yield in dairy cows.

Question 11

Why might recombinant vaccines be considered safer than some traditional vaccines?

Accepted Answer

Recombinant vaccines contain only specific antigens, reducing the risk of infection or adverse reactions.

Question 12

Which of the following correctly matches the vaccine type with its description?

Accepted Answer

Vector vaccine: uses a harmless virus or bacterium to deliver genes encoding pathogen antigens.

Question 13

A laboratory is using blue/white screening to identify E. coli colonies that have successfully taken up a recombinant plasmid. Which gene is disrupted in successful recombinants, and what is the expected colony color?

Accepted Answer

The lacZ gene is disrupted; successful recombinants form white colonies.

Question 14

During the cloning of a gene into a plasmid, which enzyme is used to join the DNA fragment and the plasmid vector, and what is the chemical reaction catalyzed by this enzyme?

Accepted Answer

DNA ligase is used; it catalyzes the formation of phosphodiester bonds between adjacent nucleotides: $$	ext{DNA-OH} + 	ext{DNA-P} ightarrow 	ext{DNA-O-P-DNA} + H_2O.$$

Question 15

A patient receives a recombinant subunit vaccine. Which of the following best describes the immune response generated by this vaccine?

Accepted Answer

The immune system is exposed to specific purified antigens, leading primarily to a humoral (antibody) response.

Question 16

Which of the following scenarios best illustrates the use of a vector vaccine?

Accepted Answer

A harmless adenovirus is engineered to express the spike protein of SARS-CoV-2, and is administered to induce immunity.

Question 17

Which of the following is a key reason why PCR is preferred over traditional cloning for rapid detection of pathogens in clinical samples?

Accepted Answer

PCR can amplify specific DNA sequences directly from small amounts of sample in a matter of hours.

Question 18

A scientist is designing a recombinant vaccine using a plasmid vector. Which of the following features should the plasmid contain to ensure successful expression of the antigen in E. coli?

Accepted Answer

A prokaryotic promoter, an origin of replication, and a selectable marker.

Question 19

Which of the following best explains why the use of Taq polymerase, rather than a typical E. coli DNA polymerase, is critical for PCR?

Accepted Answer

Taq polymerase remains active after repeated heating to $$95^\circC$$, which is required for DNA denaturation in PCR.

Microbiology Study Guide: Molecular Biology and Genetic Engineering Concepts

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