Question 1

Which of the following best describes the three primary functions of DNA in living organisms?

Accepted Answer

Storing genetic information, replicating itself, and mutating to allow variation

Question 2

Which structural feature of DNA allows it to store vast amounts of genetic information?

Accepted Answer

The sequence of nitrogenous bases along the sugar-phosphate backbone

Question 3

A DNA molecule is composed of repeating subunits called nucleotides. Which of the following correctly describes the components of a DNA nucleotide?

Accepted Answer

One phosphate group, one deoxyribose sugar, and one nitrogenous base

Question 4

Which of the following best explains why the base-pairing rules in DNA exist?

Accepted Answer

To maintain a uniform width of the double helix by pairing a purine with a pyrimidine

Question 5

If a mammal's DNA contains 20% cytosine, what percentage of its DNA is adenine?

Accepted Answer

$30\%$

Question 6

Which type of bond holds the two complementary strands of DNA together?

Accepted Answer

Hydrogen bonds between the nitrogenous bases

Question 7

Why are hydrogen bonds, rather than covalent bonds, used to join complementary bases in DNA?

Accepted Answer

Hydrogen bonds are weak, allowing the strands to separate easily during replication and transcription

Question 8

Thermophilus aquaticus is a bacterium that thrives in hot environments. How would you expect its DNA GC content to compare to that of mammals?

Accepted Answer

Higher than mammals, because GC pairs form three hydrogen bonds and provide greater thermal stability

Question 9

During DNA replication, DNA polymerase sometimes incorporates an incorrect base. What is the biological significance of this process?

Accepted Answer

It introduces mutations, which are a source of genetic variation and evolution

Question 10

If DNA polymerase never made mistakes during replication, what would be the consequence for a population of organisms?

Accepted Answer

There would be no genetic variation, preventing natural selection and evolution

Question 11

Which of the following correctly matches the nitrogenous bases with their categories?

Accepted Answer

Purines: Adenine and Guanine; Pyrimidines: Cytosine and Thymine

Question 12

Which of the following is the correct complementary DNA sequence for the strand 5'-C-A-T-3'?

Question 13

Which of the following best describes the backbone of a DNA molecule?

Accepted Answer

Repeating sugar and phosphate groups joined by covalent bonds

Question 14

Which of the following is a direct result of the semi-conservative nature of DNA replication?

Accepted Answer

Each new DNA molecule contains one original strand and one new strand

Question 15

Which of the following equations correctly represents the relationship between the percentages of the four bases in double-stranded DNA?

Accepted Answer

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

Question 16

Which of the following is NOT a reason why DNA can store a large amount of information?

Accepted Answer

The bases are covalently bonded to each other across the helix

Question 17

Which of the following is a real-world consequence of mutations in DNA?

Accepted Answer

Mutations can lead to genetic variation, which is essential for evolution and adaptation

Question 18

Which of the following statements about covalent bonds in DNA is correct?

Accepted Answer

Covalent bonds are strong and form the backbone of the DNA molecule

Question 19

Which of the following best explains why DNA is described as a double helix?

Accepted Answer

It consists of two strands twisted around each other, held together by hydrogen bonds between complementary bases

DNA Structure and Function: Study Notes for General Biology

Study Guide - Practice Questions