Which one of the following pairs of nitrogenous bases of nucleic acids, is wrongly matched with the category mentioned against it ?

$DNA$ is not directly involved with the synthesis of the following

Read the following statements and choose the set of correct statements:

$(a)$ Euchromatin is loosely packed chromatin

$(b)$ Heterochromatin is transcriptionally active

$(c)$ Histone octomer is wrapped by negatively charged DNA in nucleosome

$(d)$ Histones are rich in lysine and arginine

$(e)$ A typical nucleosome contains $400\,bp$ of DNA helix

Choose the correct answer from the options given below:

The length of a helix of $DNA$ is

In his experiments on the chemistry of $DNA$, Chargaff estimated the base composition of human sperms and found that Adenine constituted $31\%$ and Guanine $19\%$. The quantity of Cytosine in the $DNA$ of human somatic cell is likely to be