Question 1

Which of the following best explains why DNA strands are described as 'antiparallel'?

Accepted Answer

The two strands run in opposite 5’ to 3’ directions.

Question 2

A scientist analyzes a DNA sample and finds that 30% of the bases are adenine. According to Chargaff’s rules, what percentage of the bases are cytosine?

Accepted Answer

$$20\%$$

Question 3

Which of the following is a feature unique to RNA and not found in DNA?

Accepted Answer

Contains the nitrogenous base uracil.

Question 4

What type of bond is primarily responsible for holding the two strands of the DNA double helix together?

Accepted Answer

Hydrogen bonds

Question 5

Which of the following correctly lists the components of a DNA nucleotide?

Accepted Answer

Phosphate group, deoxyribose sugar, nitrogenous base

Question 6

A mutation replaces a thymine base in DNA with uracil. What is the most likely consequence?

Accepted Answer

The DNA may be recognized as damaged, since uracil is not normally found in DNA.

Question 7

Which of the following statements about the structure of DNA is FALSE?

Accepted Answer

The two strands are held together by covalent bonds between bases.

Question 8

If a segment of DNA has the sequence 5'-ATCG-3', what is the complementary sequence on the opposite strand?

Accepted Answer

3'-TAGC-5'

Question 9

Which of the following features is common to both DNA and RNA?

Accepted Answer

Both contain a phosphate group.

Question 10

A patient’s cells are found to have nucleic acid molecules with ribose sugar and uracil. Which type of nucleic acid is present?

Accepted Answer

RNA

Question 11

Which of the following best describes Chargaff’s rules?

Accepted Answer

$$\%A = \%T$$ and $$\%C = \%G$$

Question 12

Which of the following is NOT a structural feature of DNA?

Accepted Answer

Contains uracil as a nitrogenous base.

Question 13

A researcher is comparing the sugar component of DNA and RNA. Which statement is correct?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose.

Question 14

Which of the following scenarios would violate Chargaff’s rules?

Accepted Answer

A DNA sample with $$\%A = 35\%$$ and $$\%T = 20\%$$

Question 15

Which of the following best explains why the DNA double helix has a uniform diameter?

Accepted Answer

A purine always pairs with a pyrimidine.

Question 16

Which of the following is a correct comparison between DNA and RNA?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 17

A forensic scientist finds a nucleic acid sample that is double-stranded, contains deoxyribose, and has equal amounts of adenine and thymine. What is the most likely identity of this molecule?

Accepted Answer

DNA

Question 18

Which of the following is a feature unique to DNA and not found in RNA?

Accepted Answer

Contains thymine as a nitrogenous base.

Question 19

If a DNA molecule is composed of 18% guanine, what is the percentage of thymine present?

Accepted Answer

$$32\%$$

Question 20

Which of the following best describes the shape of most RNA molecules?

Accepted Answer

Randomly shaped and usually single-stranded

Nucleic Acids: Structure and Features of DNA and RNA

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