Q: A protein has a molecular weight of 60 kDa. Estimate the minimum number of base pairs required to encode this protein. (Average amino acid mass = 110 Da, 3 bp per amino acid)

$$\frac{60,000}{110} \times 3 = 1,636$$ base pairs

Question 1

Which of the following statements best describes the antiparallel nature of double-stranded DNA (dsDNA)?

Accepted Answer

One DNA strand runs 5' to 3', while the other runs 3' to 5'.

Question 2

Which chemical property of the DNA backbone contributes to its hydrophilicity?

Accepted Answer

The hydroxyl groups of the sugar residues

Question 3

Which of the following factors will increase the melting temperature ($$T_m) of a $$DNA molecule?

Accepted Answer

Increasing the percentage of G-C base pairs

Question 4

A DNA sample is denatured by heating. What is the most accurate definition of the melting temperature ($$T_m$$)?

Accepted Answer

$$T_m is $$the temperature at which half of the DNA strands are denatured.

Question 5

Which enzyme is responsible for relieving supercoiling tension in DNA during replication?

Accepted Answer

Topoisomerase

Question 6

A protein has a molecular weight of 60 kDa. Estimate the minimum number of base pairs required to encode this protein. (Average amino acid mass = 110 Da, 3 bp per amino acid)

Accepted Answer

$$\frac{60,000}{110} 	imes 3 = 1,636$$ base pairs

Question 7

Which of the following is a consensus sequence?

Accepted Answer

A sequence that represents the most common nucleotide at each position in a set of similar sequences

Question 8

Which of the following best explains the C-value paradox?

Accepted Answer

The amount of DNA per haploid cell does not always correlate with organismal complexity due to noncoding DNA.

Question 9

Which of the following is NOT a characteristic of mitochondrial DNA (mtDNA)?

Accepted Answer

It contains introns.

Question 10

Which DNA form is most commonly found in vivo under physiological conditions?

Accepted Answer

B-DNA

Question 11

Which of the following statements about DNA grooves is correct?

Accepted Answer

Major and minor grooves are sites for protein binding.

Question 12

Which of the following conditions will promote DNA denaturation?

Accepted Answer

Low pH

Question 13

If a DNA molecule has 40% G+C content, what is the expected percentage of A+T content?

Accepted Answer

60%

Question 14

Which of the following best describes the role of centromeres in eukaryotic chromosomes?

Accepted Answer

They are necessary for correct chromosome segregation during cell division.

Question 15

Which of the following is true regarding the hydrogen bonding between DNA bases?

Accepted Answer

Guanine pairs with cytosine via three hydrogen bonds.

Question 16

Which of the following statements about DNA supercoiling is correct?

Accepted Answer

Supercoiling relieves helical stress in DNA molecules.

Question 17

Which of the following is a correct estimate for the length of a DNA molecule with 10,000 base pairs? (Assume 1 helical turn = 10.4 bp, 1 turn = 33.2 Å)

Accepted Answer

$$\frac{10,000}{10.4} 	imes 33.2 \ 	ext{Å} = 31,923 \ 	ext{Å}$$

Question 18

Which of the following is NOT a difference between bacterial and eukaryotic chromosomes?

Accepted Answer

Bacterial chromosomes contain telomeres, eukaryotic chromosomes do not.

Question 19

Which of the following best describes the process of DNA renaturation?

Accepted Answer

The reassociation of complementary single DNA strands into a double helix.

Question 20

Which of the following is a property of purine and pyrimidine bases in nucleic acids?

Accepted Answer

They absorb UV light strongly at around 260 nm.

DNA: Structure, Properties, and Biological Significance

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