Question 1

Which of the following best describes the three components of a nucleotide found in nucleic acids?

Accepted Answer

A phosphate group, a five-carbon sugar, and a nitrogen-containing base

Question 2

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

Accepted Answer

DNA contains thymine, while RNA contains uracil

Question 3

What is the directionality of a nucleic acid strand, and how is it conventionally written?

Accepted Answer

From the 5' to 3' end, written as 5' → 3'

Question 4

Which of the following best explains why only purine-pyrimidine pairs fit inside the DNA double helix?

Accepted Answer

Purine-pyrimidine pairs have the correct spacing to fit between the sugar-phosphate backbones

Question 5

According to Chargaff's rules, if a DNA molecule contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

$$20\%$$

Question 6

Which of the following best describes the type of bond that links nucleotides together in a nucleic acid polymer?

Accepted Answer

Phosphodiester bond

Question 7

What is the main structural difference between ribonucleotides and deoxyribonucleotides?

Accepted Answer

Ribonucleotides have a hydroxyl group at the 2' carbon, while deoxyribonucleotides have a hydrogen at the 2' carbon

Question 8

Which of the following statements about the secondary structure of DNA is correct?

Accepted Answer

It is a double helix with antiparallel strands held together by hydrogen bonds between complementary bases

Question 9

If an E. coli chromosome contains 4 million base pairs, and half are A-T pairs, how many hydrogen bonds hold the two strands together?

Accepted Answer

$$10	ext{ million}$$

Question 10

Which of the following best explains why the addition of phosphate groups to a nucleotide raises its potential energy?

Accepted Answer

Phosphate groups are negatively charged and their repulsion stores potential energy

Question 11

Which of the following is a unique property of RNA compared to DNA?

Accepted Answer

RNA can catalyze chemical reactions (ribozymes)

Question 12

A scientist is analyzing a nucleic acid and finds that it contains uracil, is single-stranded, and can fold into complex shapes. What is the most likely identity of this molecule?

Accepted Answer

RNA

Question 13

Which of the following best describes the process by which nucleotides are joined together to form nucleic acids?

Accepted Answer

A condensation reaction forms a phosphodiester linkage, releasing $$\mathrm{H_2O}$$

Question 14

Which of the following base pairs is stabilized by three hydrogen bonds in DNA?

Accepted Answer

Guanine and cytosine

Question 15

Which scientist(s) are credited with building the first accurate model of the DNA double helix?

Accepted Answer

James Watson and Francis Crick

Question 16

Which of the following best explains why DNA is soluble in water?

Accepted Answer

The sugar-phosphate backbone is hydrophilic

Question 17

A mutation causes a DNA strand to have two purines paired together. What is the most likely structural consequence?

Accepted Answer

The double helix will bulge at the site of the mutation

Question 18

Which of the following best describes the secondary structure of RNA?

Accepted Answer

Single-stranded regions fold to form stem-loops (hairpins) via complementary base pairing

Question 19

Which of the following is a real-world application of the ability of DNA to store and transmit biological information?

Accepted Answer

DNA fingerprinting in forensic science

Question 20

Which of the following best explains why the condensation reaction that forms phosphodiester bonds is not energetically favorable unless nucleotide triphosphates are used?

Accepted Answer

The hydrolysis of the extra phosphate groups in nucleotide triphosphates provides the energy needed for bond formation

Nucleic Acids and the RNA World: Structure, Function, and Biological Significance

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