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Walter Ogston ogston at HOBBES.KZOO.EDU
Tue Feb 28 14:31:49 EST 1995

Patrick O'Neil <patrick at corona> writes:
[stuff deleted]
> Retroviruses are also permanent riders.  Once one enters, it becomes a 
> part of your genome.  As a matter of fact, vertebrate genomes are 
> littered with ancient, endogenous retroviruses.  
This statement is only partly correct.  When a retrovirus
infects a cell it integrates into the genome of the cell, not
into the genome of the whole host animal.  The distinction
between germ-line and soma applies here.  The integrated
retrovirus from an infected somatic cell cannot be passed on to
offspring, and does not become an endogenous retrovirus.  

The endogenous retroviruses originate from the very rare
occasions when a germ-line cell is infected.  Germ cells of the
adult are probably resistant to infection, but one instance of a
new endogonous virus being produced occurred in experimental
infection of a pregnant mouse with Moloney Murine Leukemia
Virus.  One offspring of this mouse carried a new endogenous
provirus that disrupted a collagen gene.  You can read about
this in a paper by R. Jaenisch, Proc. Natl. Acad. Sci. 73:1260
(1976) and subsequent papers by Jaenisch and his lab.  

Aren't these critters fascinating? :)
Walter Ogston				ogston at
Department of Biology			Phone: (616)337-7010
Kalamazoo College			Fax:   (616)337-7251
Kalamazoo, MI 49006-3295

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