How many polynucleotide chains are present in the structure of $DNA$?

Identify $X$ and $Y$ in the given diagram of a nucleosome.

Telomerase is an enzyme that is a/an ....

The linkage between two nucleotides occurs between the $3'$ carbon of the sugar of the first nucleotide and the $5'$ carbon of the sugar of the second nucleotide. Which of the following correctly represents these positions?

$DNA$ strands are antiparallel because of the presence of

Identify the complementary nitrogenous base for the adenine nitrogenous base in the structure of $DNA$.