Genes are chemically

Erwin Chargaff $(1950)$ estimated that . . . . . . .

Assertion : In a $DNA$ molecule,$A-T$ rich parts melt before $G-C$ rich parts.
Reason : In between $A$ and $T$ there are three $H-$ bonds,whereas in between $G$ and $C$ there are two $H-$ bonds.

Which of the following features provide stability to the helical structure of $\text{DNA}$?

How many nucleotides are present in one turn of $DNA$ helix (in $pairs$)?

How many base pairs are present in each turn of the $DNA$ helix?