Human chimeras

[tonygraham]

Did anybody else see this in The New Scientist? Unfortunately, I'm having trouble with my online access, so I can't be too specific on the details at the moment but the thrust of it was that a large number of people may be carrying more than one genetic code.

Apparently, what happens is that non-identical twins merge at the blastula (ball of cells) stage and cells from each then go on to develop into different tissues. So it is possible that the cells of your kidney are carrying a different set of genes from the set your liver cells are carrying, for example.

This has obvious and profound implications for a variety of subjects - paternity testing, individualised medicines, forensics, etc.

If I remember correctly, it came to light following something like a paternity test, during which DNA comparison showed that the mother couldn't be a parent of the child, which she definitely was. When they tested her DNA using a sample of a different tissue, they found a different gene makeup.

Interesting, eh?

 

[geni]

They were also argueing that everyone was to some degree a chimera. And that in some way this was binficial for your health.

 

[davidhorman]

Yeah... there was something not too long ago about scientists creating chimeras of rabbits and humans - they didn't let them go any further than a small number of cells.

There are pictures out there of sheep/goat chimeras, which are patchy-skinned animals that look halfway between. It seems human chimerism could explain how some men have different blood and semen types (e.g. Russian serial killer Andrei Chikatilo).

Here's some more stuff: http://www.nature.com/nsu/020429/020429-13.html

Twin embryos often share a blood supply in the placenta, allowing blood stem cells to pass from one embryo and settle in the bone marrow of the other, seeding a lasting source of blood. As a result, as many as 8% of non-identical twin pairs have chimaeric blood.

Patchy diseases, in which only regions of tissue are affected, might be caused by mosaicism (a mutation occurs early on and makes the foetus a sort of chimera with itself, if I understood correctly). Another telltale sign of the condition is a characteristic variation in skin pigmentation that causes patterns called Blaschko's lines, including V-shaped streaks on the back that are sometimes only visible under ultraviolet light.

When I get home I'm getting myself in front of the mirror with a UV light

David

 

[Reginald]

Yes as I understand it they checked her for a tissue match, found that although the children were not "her's" that they were of her family. She is theoretically the product of four sex cells, 2 male, 2 female.

It's not common but there is more here from Nature.

Human genetics: Dual identities

Edited to add ^^^^^^^^ he beat me to it!

 

[Suezoled]

I wonder how this would affect the screening process for organ transplants selection?

 

[EvilYeti]

Oh crap, I smell a new Crichton novel!