Question

In DNA molecule, which of the following base pair is not present?

• A. Cytosine and adenine
• B. Adenine and thymine
• C. Adenine and guanine
• D. Cytosine and thymine

Answer 1

Answer: (A), (C), (D)

Adenine and guanine
Cytosine and thymine
Cytosine and adenine

• In DNA, four bases pairs- adenine (A), cytosine (C), guanine (G), and thymine (T) are present. Uracil substitutes Thymine in RNA and is absent in DNA.
• The double strands of DNA are held together by hydrogen bonds between the bases, adenine forms a base pair with thymine (2 hydrogen bonds), and cytosine forms a base pair with guanine (3 hydrogen bonds).
  
• Thus, Options (A) Cytosine and adenine, (C) Adenine and guanine, (D) Cytosine and thymine do not form base pairs in DNA.