A double stranded DNA fragment has 500 Adenine bases. If total number of base pairs in this fragment is 2500, then what will be the number of guanine bases?

750

The correct answer is Option (2) → 750

In a double-stranded DNA molecule, Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C). Therefore, the number of Adenine bases equals the number of Thymine bases, and the number of Guanine bases equals the number of Cytosine bases.

Given:

• Total base pairs = 2500
• Adenine bases = 500

Solution:

Since there are 500 Adenine bases, there are also 500 Thymine bases (A = T pairing).

So, the total number of A-T pairs = 500 + 500 = 1000.

The remaining base pairs must be G-C pairs.

• Total base pairs - A-T pairs = G-C pairs
• 2500−1000=1500 G-C pairs

Thus, the number of Guanine bases is half of the G-C pairs:

\(\frac{1500}{2}\)=750

The number of Guanine bases is 750.