Explain the genetic implication of the structure of $DNA$.

(N/A) The base pairing confers a unique property to the polynucleotide chains.
Both polynucleotide chains are complementary to each other. Therefore,if the sequence of bases in one strand is known,the sequence of bases in the other strand can be predicted.
If each strand of $DNA$ (parent $DNA$) acts as a template for the synthesis of a new strand,the two double-stranded $DNA$ molecules (daughter $DNA$) produced would be identical to the parent $DNA$ molecule.
The main features of the double-helical structure of $DNA$ are as follows:
$(1)$ $DNA$ is made of two polynucleotide chains. Its backbone is constituted by sugar-phosphate,and the nitrogenous bases project inside.
$(2)$ The two chains have anti-parallel polarity. It means,if one chain has the polarity $5' \rightarrow 3'$,the other has $3' \rightarrow 5'$.
$(3)$ The nitrogenous bases in the two strands are paired through hydrogen bonds forming base pairs. Adenine forms two hydrogen bonds with Thymine from the opposite strand and vice-versa. Similarly,Guanine is bonded with Cytosine by three hydrogen bonds.
$A = T, G \equiv C$
This results in a uniform distance between the two strands.
$(4)$ The two chains are coiled in a right-handed fashion. The pitch of the helix is $3.4 \ nm$ (a nanometre is $10^{-9} \ m$) and there are roughly $10 \ bp$ in each turn. Consequently,the distance between a base pair in a helix is approximately $0.34 \ nm$.