Question

If there are four AT base pairs in one spiral (gyro) of DNA, the total number of hydrogen bonds present between the two strands in the spiral is

• A. 24
• B. 26
• C. 30
• D. 20

Answer 1

The correct option is B 26

• Each spiral of DNA consists of ten base pairs.
• Here, it is mentioned that there are four AT ( Adenine-Thymine ) base pairs in one spiral. It means rest of the base pairs of spiral DNA are GC ( Guanine-cytosine ).
• Each AT base pair is bonded by double hydrogen bond while each GC base pair is bonded by triple hydrogen bond. Hence, this spiral consist of 4*2 + 6*3 = 26 hydrogen bonds.
• So, the correct answer is '26'.