What is formed when a deoxyribose sugar combines with a nitrogenous base?

One turn of the helix in a $B$-form $DNA$ is approximately (in $nm$)

In sea urchin $DNA$,which is double stranded,$17\%$ of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this $DNA$ are

What are the full forms of $mRNA$ and $tRNA$?

Which amino acids are present in high amounts in histone proteins?

Which of the following are the complementary base pairs found in the structure of $DNA$?