Which of the following are pyrimidines?

What is the length of $DNA$ present in a nucleosome (in $, nm$)?

Read the following statements and choose the set of correct statements:
$(a)$ Euchromatin stains light.
$(b)$ Heterochromatin is transcriptionally inactive.
$(c)$ Histone octamer contains eight molecules of histone proteins.
$(d)$ Packaging of chromatin at higher level requires additional set of proteins that are referred to as non-histone chromosomal $(NHC)$ proteins.
$(e)$ In a human diploid cell,$6.6 \times 10^9$ base pairs are present,not $6.6 \times 10$ nucleosomes.
Choose the correct answer from the options given below:

Thymine is which type of nitrogenous base?

$DNA$ elements, which can switch their position, are called:

If a length of $DNA$ has $45,000$ base pairs,how many complete turns will the $DNA$ molecule take?