Which nitrogenous base is $NOT$ present in $DNA$?

If the base sequence in one strand of $DNA$ is "$ATCGA$", what is the total number of $H$-bonds present in the $DNA$ double helix?

What is the reason for the anti-parallel nature of $DNA$ strands?

In an experiment,$DNA$ is treated with a compound that intercalates between the stacks of nitrogenous base pairs. As a result,the distance between two consecutive base pairs increases from $0.34 \, nm$ to $0.44 \, nm$. Calculate the length of the $DNA$ double helix (which has $2 \times 10^9 \, bp$) in the presence of a saturating amount of this compound. (in $m$)

Nucleosomes are

If $A$ and $C$ make $30\%$ and $20\%$ of $DNA$,respectively,what will be the percentage composition of $T$ and $G$?