Structure of DNA Bases

DNA, the genetic material of all living organisms, is a polymer that consists of four different types of molecular units, or bases, connected to a chemical backbone. Shown here are the four bases adenine, thymine, guanine and cytosine. Carbon atoms are represented by grey spheres, nitrogen atoms are shown in blue, hydrogen in white, and oxygen in red. Within the DNA helix, adenine always pairs with thymine and guanine always pairs with cytosine.

Question 1: What are the four bases of DNA?
  1. A,B,C,D
  2. A,C,G,T
  3. G,A,C,U
  4. C,A,T,X


Answer 1

Answer - (b) A,C,G,T

Question 2: Adenine always pairs with _________ in DNA.
  1. Guanine
  2. Cytosine
  3. Thymine
  4. Adenine


Answer 2

Answer - (c) Thymine

Question 3: Guanine always pairs with _________ in DNA.
  1. Guanine
  2. Cytosine
  3. Thymine
  4. Adenine


Answer 3

Answer - (b) Cytosine