Question 1

Which of the following best describes the principle behind the Sanger (chain-terminator) method of DNA sequencing?

Accepted Answer

The incorporation of dideoxynucleotide triphosphates (ddNTPs) to terminate DNA chain elongation at specific bases.

Question 2

In the Sanger sequencing method, what is the role of the 3'-hydroxyl group on the growing DNA strand?

Accepted Answer

It reacts with an incoming deoxynucleoside triphosphate (dNTP) to form a new phosphodiester bond.

Question 3

Which equation correctly represents the formation of a phosphodiester bond during DNA synthesis?

Accepted Answer

$$dNTP + (DNA)_{n} \rightarrow (DNA)_{n+1} + PP_i$$

Question 4

Why are four separate reaction mixtures used in traditional Sanger sequencing?

Accepted Answer

To ensure each mixture contains a different ddNTP, allowing termination at each of the four bases.

Question 5

What is the function of plasmid vectors in molecular cloning?

Accepted Answer

To carry and replicate foreign DNA segments in host cells.

Question 6

Which selectable marker is commonly used to identify bacteria that have taken up a plasmid vector?

Accepted Answer

Ampicillin resistance gene (Amp^r).

Question 7

If a plasmid vector with an intact lacZ gene is introduced into E. coli and grown on X-Gal, what color will the colonies be?

Accepted Answer

Blue

Question 8

What is the main advantage of using restriction enzymes in recombinant DNA technology?

Accepted Answer

They allow precise excision and insertion of DNA fragments at specific sites.

Question 9

Which process describes the introduction of recombinant DNA into a bacterial host cell?

Accepted Answer

Transformation

Question 10

During automated DNA sequencing, how are the fragments detected and analyzed?

Accepted Answer

By separating fragments by size and detecting fluorescence at the 3' end.

Question 11

Which of the following best explains why dideoxynucleotides (ddNTPs) terminate DNA synthesis?

Accepted Answer

They lack a 3'-hydroxyl group, preventing formation of a phosphodiester bond.

Question 12

Which equation represents the termination of DNA synthesis by ddNTPs?

Accepted Answer

$$(DNA)_{n} + ddNTP \rightarrow (DNA)_{n+1}^{terminated}$$

Question 13

What is the purpose of using X-Gal in screening for recombinant plasmids?

Accepted Answer

To distinguish between bacteria with intact and disrupted lacZ genes based on colony color.

Question 14

Which of the following steps is NOT part of the process for expressing DNA of interest in cells?

Accepted Answer

Sequencing the DNA using the Sanger method.

Question 15

In the context of cloning, what does the term 'vector' refer to?

Accepted Answer

A DNA molecule used to carry foreign DNA into a host cell.

Question 16

Which host organism is commonly used for producing large amounts of inserted DNA in cloning experiments?

Accepted Answer

E. coli

Question 17

What is the main purpose of creating transgenic mice in genetic engineering?

Accepted Answer

To study gene expression and function under controlled conditions.

Question 18

Which of the following is a correct description of molecular cloning?

Accepted Answer

The production of multiple identical organisms derived from a single ancestor.

Question 19

What is the function of DNA ligase in recombinant DNA technology?

Accepted Answer

To join DNA fragments by forming covalent bonds between sugar-phosphate backbones.

Nucleic Acids: Sequencing and Manipulation

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