Ian A. York (york at mbcrr.dfci.harvard.edu) wrote:
: In article <Cy24L5.H9t at eecs.nwu.edu> markb at hook.eecs.nwu.edu (Mark E. Brodsky) writes:
: >Recently, I was browsing a Virology WWW page, when I came across a
: >referance to "Diploid" viruses. It seemed to imply that these were not
: >diploid in the usual sense of the word, but the server did not
: >elaborate any more on the subject. Could someone please explain what
: >is meant by a diploid virus? Thank you.
: I'm not sure if this is what was meant, but herpes simplex virus (and
: most of the other herpes viruses) are pseduodiploid for some of their
: genes. This is because their genome contains repeated regions which
: encode a couple of genes: (ascii herpes simplex virus: not to scale)
: ____ ________ __
: ^^^^^^ b k ^^^^^^^^^^ ^^^^
: gene a a ^^^^^ ^^^^
: l m t l
: As this schematic is supposed to show, genes "a" and "l" are doploid,
: while genes "b" to "k" and "m" to "t" are not.
: Hope this helps.
Furthermore, the retrovirus particles contain two copies of the genomic
RNA. They will be "homozygous" if originating from a cell with only one
provirus, and may be "heterozygous" when incorporating transcripts from
two different proviruses (probably random) in a mixed infection setting.
Recombination between the two copies seems to happen frequently.
Orthomyxovirus particles like influenza virus, which has its genome
ditributed over nine RNA segments also seem to package more than nine RNA
molecules, resulting in diploidy or oligoploidy for some genes, and
perhaps omission of one or several genome segments in some particles.
This is perhaps a rather slack mechanism to ensure that most particles
contain a complete set.
I have the impression that there is great variation among the viruses in
how stringently they package their genomes and exclude other genetic
Olav Hungnes olav.hungnes at embnet.uio.no
National Institute Phone (+47)22042200
of Public Health FAX (+47)22353605