General index
Polynucleotides
Two nucleotides can be linked through a phosphodiester bond. A number of
nucleotides linked by phosphodiester bonds constitute a Polynucleotide. As in the case
of proteins, it is usual not to represent hydrogen atoms in polynucleotides. Let's see a Nucleoside:
Being a deoxynucleoside, it can be esterified in 3' and 5'. Let's suppose that it is esterified in 3':
We then have on display a Tetranucleotide. By convention, polynucleotides are
numbered from the 5'-terminal residue, that has a free 5'-OH group (5'-end):
5'- ACGC - 3'
Or simply, ACGC. Note that the degree of polymerization of polynucleotides can be
very high, with hundreds of millions of nucleotides in genomic DNA's. Let´s see the Nucleosome DNA
(an eukaryotic genome can contain millions of nucleosomes: