The double-helical structure of $DNA$ discovered by Watson and Crick is known as .....

Match the number of nucleotides of the genome in Column $I$ with the organisms in Column $II$. Choose the correct option given below.

Column $I$	Column $II$
$(A) 5386$ nucleotides	$(p) E. coli$
$(B) 48502$ bp	$(q) \text{Man}$
$(C) 4.6 \times 10^6$ bp	$(r) \text{Drosophila}$
$(D) 3.3 \times 10^9$ bp	$(s) \phi \times 174 \text{ bacteriophage}$
	$(t) \text{Bacteriophage lambda}$

What is the full form of $NHC$?

How is the $DNA$ molecule useful to higher organisms?

Identify the given nitrogenous bases $P$ and $Q$.

In $DNA$,uracil is replaced by