Question

Two DNA strands have the same length. Which one will denature at a lower temperature?

• A. The one having more number of guanine and cytosine molecules
• B. The one having more number of adenine and thymine molecules
• C. The one having least number of guanine and cytosine molecules
• D. More than one option is correct

Answer 1

Answer: (D)

In a double helix structure of DNA, the bases in the two complementary strands are paired with the help of hydrogen bonds. There are two hydrogen bonds between one adenine and thymine base pairs whereas there are three hydrogen bonds between one guanine and cytosine base pairs. The energy required to break the bond between G-C will be more as compared to energy required for A-T bonds. So the DNA with a maximum number of A-T pairing will melt faster at lower temperature as compared to others.