Which one of the following shows a clover leaf model?

In the structure of $DNA$,a purine base of one nucleotide is linked to a pyrimidine base of the opposite nucleotide by which type of bond?

Which one of the following statements about Histones is wrong?

The length of $DNA$ having $23$ base pairs is:

What is a template?

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.