Index >> Virus Structure and Classification >> Terminal Redundancy of Some Virus

Terminal Redundancy of Some Viruses - The DNA of Some contains repeated nucleotide sequences at its terminus.

This is viruses known as terminal redundancy. Thus in the T-even phages bout 5% of the total molecule is repeated at the ends. Terminal redundancy is of many types.

The DNA of herpesvirus has a repeated sequence of about 800 base pairs, which represents about 0.5% of the total DNA.

3’ a-b-c------------------x-y-z-a-b-c 5’

5’ a-b-c------------------x-y-z-a-b-c 3

Here a-a' represent complementary nucleotides.

In adenovirus also there terminal redundancy, but the DNA shows inverted repetition.

a-b-c - - - - - - c'-b'-a"

a'-b' -c' - - - - - -c-b-a

In the lambda phage of E. coli the DNA is linear double helical, except for a, single stranded region, 12 nucleotides long, on each strand. The single stranded regions are at opposite ends, and are complementary. Base pairing between these regions results in the formation of a closed ring.

The single stranded regions are therefore called cohesive ends or 'sticky' ends.