1. The two helical polynucleotide chains are coiled around a common axis. The two chains have opposite polarity i.e. they are antiparrallel.

2. The regular repeating sugar phosphate backbone of each strand lies on the outside of the helix. The purine and pyrimidine bases project inwards at 900 to the axis of the helix.

Some common words found in the essay are:
, Nitrogen-Containing Bases, Pentose Sugar, RNA DNA, condensation reactions, purine bases, acids contain sugar, acids contain, hydrogen bonds, contain sugar, bases nitrogen, pyrimidines cytosine, nucleic acids,
Approximate Word count = 421
Approximate Pages = 2 (250 words per page double spaced)