Mutation of $DNA$ occurs due to changes in the sequence of one of the following:

The double helical structure of $DNA$ was proposed by

$ADP$ and $ATP$ differ in the number of

Which of the following bases is a purine derivative?

$A$ nucleic acid,whether $DNA$ or $RNA$,gives on complete hydrolysis,two purine bases,two pyrimidine bases,a pentose sugar,and phosphoric acid. Nucleotides,which are intermediate products in the hydrolysis,contain:

The two strands in $DNA$ are not identical but are complementary. Explain.