Question 1

Which of the following best describes the function of restriction endonucleases in molecular biology?

Accepted Answer

They cut double-stranded DNA at specific base-pair sequences known as recognition sites.

Question 2

A restriction enzyme recognizes the sequence $$5'-GAATTC-3'$$ and cuts between G and A. If a DNA molecule contains 12,288 base pairs, how many cuts would you expect this enzyme to make, assuming random base distribution?

Accepted Answer

$$3$$

Question 3

Why are sticky ends produced by restriction enzymes more useful for molecular cloning than blunt ends?

Accepted Answer

Sticky ends allow for easier and more specific annealing of complementary DNA fragments.

Question 4

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 5

During gel electrophoresis, why do shorter DNA fragments migrate further than longer fragments?

Accepted Answer

Shorter fragments can move more easily through the pores of the gel matrix.

Question 6

A plasmid is used as a vector in genetic engineering. Which property makes plasmids especially useful for this purpose?

Accepted Answer

They are small, circular DNA molecules that can replicate independently of the bacterial chromosome.

Question 7

What is the role of methylases in bacterial cells?

Accepted Answer

They add methyl groups to the host DNA to protect it from cleavage by restriction enzymes.

Question 8

In the polymerase chain reaction (PCR), why is Taq polymerase used instead of DNA polymerase III?

Accepted Answer

Taq polymerase is stable at the high temperatures required for DNA denaturation.

Question 9

Which of the following best explains why a two-base-pair recognition site for a restriction enzyme would be less useful in genetic engineering than a six-base-pair site?

Accepted Answer

A two-base-pair site would occur too frequently, resulting in too many cuts and fragmentation of the DNA.

Question 10

A bacterium is described as 'competent.' What does this mean in the context of genetic engineering?

Accepted Answer

It is able to take up foreign DNA from its environment.

Question 11

Which of the following is a direct application of PCR in forensic science?

Accepted Answer

Amplifying small amounts of DNA from crime scene evidence for analysis.

Question 12

If a restriction enzyme recognizes an 8-base-pair sequence, what is the expected frequency of cuts in a random DNA sequence?

Accepted Answer

$$1 in $$every $$4^8 = 65$$,536$$ base pairs

Question 13

Which of the following best describes the process of transformation in bacteria?

Accepted Answer

The uptake and incorporation of foreign DNA (such as a plasmid) into a bacterial cell.

Question 14

A scientist wants to separate DNA fragments of different lengths. Which technique should they use?

Accepted Answer

Gel electrophoresis

Question 15

Which of the following is a reason why the lac operon is considered an example of negative regulation?

Accepted Answer

The absence of lactose allows the repressor protein to bind the operator and block transcription.

Question 16

Which of the following best explains why C4 plants are more efficient than C3 plants in hot, dry environments?

Accepted Answer

C4 plants concentrate CO2 at the site of rubisco, reducing photorespiration.

Question 17

Which of the following is a direct result of the action of the enzyme ATP synthase during cellular respiration?

Accepted Answer

The synthesis of ATP from ADP and Pi using the energy of a proton gradient.

Question 18

Which of the following statements about the electron transport chain (ETC) in mitochondria is correct?

Accepted Answer

Oxygen acts as the final electron acceptor, forming water.

Question 19

Which of the following best describes the difference between substrate-level phosphorylation and oxidative phosphorylation?

Accepted Answer

Substrate-level phosphorylation directly transfers a phosphate group to ADP, while oxidative phosphorylation uses a proton gradient and ATP synthase.

Molecular Tools and Techniques in Biotechnology: Restriction Enzymes, Gel Electrophoresis, Plasmids, and Genetic Engineering

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