Question

In a double helix model of DNA, how far is each base pair from the next base pair?

• A. $20nm$
• B. $0.34nm$
• C. $34nm$
• D. $3.4nm$

Answer 1

The correct option is B $0.34nm$

Part 1: Watson and Crick Model of DNA double helix
According to Watson and Crick’s model of double helical DNA -
● One turn of DNA helix has $10$ nucleotides or $10$ base pairs
● Length of one complete turn of the DNA double helix is $34\dot{A}=3.4nm$
● Length between two adjacent base pairs $=\left(\frac{3.4}{10}\right)nm=0.34nm$


Final answer
$0.34nm$