Q: Which of the following equations correctly represents the hydrogen bonding between DNA bases?

$$\text{A} + \text{T} \rightarrow 2 \text{ hydrogen bonds}$$

Question 1

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

Accepted Answer

They terminate DNA strand elongation due to the absence of a 3'-OH group.

Question 2

A researcher wants to amplify a specific DNA fragment using PCR. Which of the following steps is NOT part of a typical PCR cycle?

Accepted Answer

Ligation of DNA fragments by DNA ligase.

Question 3

Restriction enzymes such as EcoRI recognize specific DNA sequences and cleave them. What is the sequence recognized by EcoRI, and what type of ends does it produce?

Accepted Answer

GAATTC; sticky ends

Question 4

During solid-phase oligonucleotide synthesis by the phosphoramidite method, which step ensures the formation of a stable phosphodiester bond?

Accepted Answer

Oxidation step

Question 5

Which of the following statements about DNA and RNA is CORRECT?

Accepted Answer

Both DNA and RNA are polymers of nucleoside 5'-phosphates connected by 3'-5' phosphodiester bonds.

Question 6

A scientist uses site-directed mutagenesis to change a single base in a gene. Which tool is most critical for introducing the mutation?

Accepted Answer

A mismatched synthetic oligonucleotide primer

Question 7

In gel electrophoresis, DNA fragments are separated based on which property?

Accepted Answer

Size (length in base pairs)

Question 8

Which of the following best explains why ethidium bromide is used in DNA gel electrophoresis?

Accepted Answer

It intercalates between aromatic bases and fluoresces under UV light.

Question 9

A DNA molecule is described as having a 'palindromic' sequence. What does this mean?

Accepted Answer

The sequence reads the same on both strands in the 5' to 3' direction.

Question 10

Which of the following equations correctly represents the hydrogen bonding between DNA bases?

Accepted Answer

$$	ext{A} + 	ext{T} ightarrow 2 	ext{ hydrogen bonds}$$

Question 11

During PCR, why is a thermostable DNA polymerase such as Taq polymerase used?

Accepted Answer

It remains active after repeated heating cycles required for DNA denaturation.

Question 12

Which of the following best describes the semiconservative mechanism of DNA replication?

Accepted Answer

Each daughter DNA molecule contains one parental and one newly synthesized strand.

Question 13

A scientist is using the Sanger method to sequence DNA. What would happen if only dNTPs (no ddNTPs) were present in the reaction?

Accepted Answer

DNA synthesis would continue without termination, producing only full-length products.

Question 14

Which of the following is a key difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose.

Question 15

Which of the following best describes the function of a primer in DNA sequencing or PCR?

Accepted Answer

It provides a free 3'-OH group for DNA polymerase to extend.

Question 16

A researcher is cloning a gene into a plasmid vector. Which enzyme is required to join the gene fragment to the plasmid?

Accepted Answer

DNA ligase

Question 17

Which of the following is a real-world application of site-directed mutagenesis?

Accepted Answer

Creating a specific amino acid substitution in an enzyme to study its function.

Question 18

Which of the following best explains why energy is required to separate the double helical structure of DNA?

Accepted Answer

Hydrogen bonds between complementary bases must be broken.

Question 19

Which of the following is a correct representation of the phosphodiester bond in nucleic acids?

Accepted Answer

$$	ext{3'-OH of one nucleotide} + 	ext{5'-phosphate of next nucleotide} ightarrow 	ext{phosphodiester bond}$$

Manipulating DNA: Tools and Techniques in Nucleic Acid Biochemistry

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