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,