Question 1

Which of the following correctly identifies the five nitrogenous bases shown in the image, from left to right, top row first, then bottom row?

Accepted Answer

Cytosine, Thymine, Uracil, Guanine, Adenine

Question 2

Based on the structures shown, which of the following statements is TRUE regarding purines and pyrimidines?

Accepted Answer

Purines include adenine and guanine, which have a double-ring structure.

Question 3

Which base is found only in RNA and not in DNA, as shown in the image?

Accepted Answer

Uracil

Question 4

Which of the following bases pairs with cytosine in DNA, and how many hydrogen bonds are formed between them?

Accepted Answer

Guanine; 3 hydrogen bonds

Question 5

If a DNA molecule contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 6

Which of the following best describes the difference between thymine and uracil, as seen in their chemical structures?

Accepted Answer

Thymine has a methyl group at the 5' position, while uracil does not.

Question 7

Which of the following bases is NOT a pyrimidine?

Accepted Answer

Adenine

Question 8

Which of the following statements about the nitrogenous bases is correct?

Accepted Answer

Guanine and adenine are both purines.

Question 9

If a mutation replaces a cytosine with a thymine in DNA, what type of mutation is this?

Accepted Answer

Transition

Question 10

Which of the following best explains why DNA is more stable than RNA?

Accepted Answer

DNA contains deoxyribose, which lacks a 2' hydroxyl group, making it less susceptible to hydrolysis.

Genetics Study Guide: DNA, Chromosomes, and Nucleic Acid Structure

Study Guide - Practice Questions