DNA and genomes

The Phosphodiester bond allows nucleotides to polymerise and form a DNA strand.

It is a bond between 2 nucleotides of the hydroxyl (OH) group of the 3' carbon from a nucleotide, and of the phosphate group of the 5' carbon from the next nucleotide.

A chain or (strand) of DNA is thus obtained.

Note: nitrogenous bases are not part of a phosphodiester bond.

A DNA strand has two ends, each with very different properties:

• 5' end free phosphate (the first nucleotide)

• 3' end free hydroxyl group (the last nucleotide)

By convention, a DNA strand is always read from 5' to 3'.