18-11-1985
Dear
Bill,
I’m
afraid your article is a bit out of my depth as well but I’ve made a few
enquiries at work which should help.
A
retrovirus is simply a class of virus, while endogenous means that the genome
(or chromosomes) of that virus had once got into the cells of the chicken and
stayed there by becoming part of a chicken chromosome. Once part of a chicken
chromosome this part of virus is then inherited by future generations.
Apparently it doesn’t actually do anything but is simply stuck there as part
of the chicken cell.
The
80% homology in both the Red Jungle Fowl and the chicken have this part of
virus in the 80% of individuals. The Grey Jungle Fowl population however has
it only 10% of the individuals.
Restriction
enzyme digestion is a method of breaking chromosomes into smaller pieces of
DNA. It’s apparently the basis of a lot of genetic engineering techniques.
By this method they have shown that identical pieces of viral DNA (part of
viral chromosomes) exist in the chromosomes of both the Red Jungle Fowl and
the chicken, but not in any of the other species of Jungle Fowl.
All
this has led the authors to think that this part of virus found its way into
the Red Jungle Fowl after it had become a separate species to the other Jungle
Fowls (which is why they don’t have it) but before any Red Jungle Fowl were
domesticated.
The
presence of identical pieces of virus in the same proportions of individuals
in both the Red Jungle Fowl and the domestic chicken suggests that they both
have common ancestors in the not too distant past.
I
hope this will be of some use to you. I’m afraid I’ll be in England for 7
weeks as from the 23th
of November so unless the post is very quick I may not be able to clear up any
thing that I haven’t explained very well. Ros Ryan at the Black Hill
laboratory would be your best bet for any more help that he’s extremely
difficult to catch these days: he’s one of the Directors.
Yours
sincerely,