..............is common for both $DNA$ and $RNA$ but.............is present only in $DNA$

Nucleotides are linked by

$DNA$ is transcribed by some viral $RNA$ using the enzyme

By using diagram, select the correct option for $X$ and $Y$

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  distancebetween two consecutive base increases. from $0.34- 0.44\,nm$ calculate the length of $DNA$ double helix $($ which has $2 \times 10^9\,bP)$ in the presence of saturating amount of this compound.

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 $6.6 \times 10^{9}$ $bp,$ then the length of the $DNA$ is approximately