# NEET BIOLOGY

## GENETICS AND EVOLUTION

### MOLECULAR BASIS OF INHERITANCE

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
The distance between a base pair in a helix is approximately ____
 A 0.34 nm B 3.4 nm C 34 nm D 0.034 nm
Explanation:

Detailed explanation-1: -If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6×109 bp, then the length of the DNA is approximately. No worries!

Detailed explanation-2: -The two antiparallel polynucleotide chains of DNA are coiled around the same axis while bases are present at a right angle to the axis. Since, one complete turn of the double helix is 3.4 nm long and each of which has 10 base pairs, the distance between two consecutive base pairs 0.34 nm.

Detailed explanation-3: -In an experiment, DNA is treated with a compound which tends to place itself amongst the stacks of nitrogenous base pairs. As a result of this, the distance between two consecutive bases increases, from 0.34 nm to 0.44 nm.

Detailed explanation-4: -Solution : B-DNA is helical structure with 20 ‘Å‘ diameter and the distance between the two base pairs is 3.4 ‘Å‘ and there are 10 base pairs in each turn or pitch (one round). Hence, one turn of the helix is approximately 34 ‘Å‘ or 3.4 nm (10 ‘Å‘ = 1.0 nm).

Detailed explanation-5: -Each turn of the DNA helix is called the pitch, and it is about 34 Angstrom or 3.4 nm in length and approximately has 10 base pairs.

There is 1 question to complete.