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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:




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