Inbreeding/genetic issue?

[Jono]

Inbreeding, or even Incest: Does not cause genetic defects. What happens is that relatives are likely to have similar defects on the DNA. So if the same chromosome (with the same defect) come together in child, this child may show deviances due to defective DNA.

Read this from a bloke just recently.

Any comment on this?

 

[athon]

Sure. What's the problem with it?

Everybody has two 'sets' of genes that have similar codes. One set is from Ma, the other Pa. It's an advantage for sexual organisms to have this for two reasons; one, for variation (some combinations might be better than others). Two, if one variation of a gene is broken, the other copy might well work.

Thing is, if you have a broken copy, you might well have inherited from Ma or Pa. One of your siblings might well have it, too. That's fine if you have a broken copy, because if you pass it on to your own offspring, they will probably get a working version from the other parent you've mated with. But, if you do the deed with somebody who has a higher chance of also having a broken copy...

Inbreeding has been used for centuries to make numerous copies of 'preferential' traits in animals. It doesn't make mutations; it just makes it more likely that you will express a recessive (broken) gene.

Athon
(BTW, I think this belongs in the science forum)

 

[sophia8]

I remember reading about a German colony in South America that illustrates this. This group of 200 or so had moved there in the late 19thC and started an Amish-type farming community. Their rules forbade them from marrying outside the community (they were surrounded by native peoples, and apparently had a horror of miscagenation). So in a couple of generations they were all marrying their cousins/uncles/aunts. Over the generations fertility declined, more and more retarded and disabled children were being born and people were leaving to find partners. By the 1990s, the colony consisted of a few dozen aging people and a few retarded younger people.
A grim warning about keeping to racial purity.

 

[Chris Haynes]

Hmmmm... sounds like Colonia Tovar... but when we were there in the 1970's it was a booming tourist trap. I didn't get to go, since my parents went to an adult only trip there (though I did get to go on a field trip to the Arte Morano glass studio, founded by a group of Italian artisens).

Here: http://www.venezuelaturistica.com/ICTovar.htm ... it opened up about a century after it was founded. So there were some genetic anomalies, and they have been studied:
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=14617047&dopt=Abstract

Another more intriguing look into genetics would be Oliver Sacks' book The Island of the Colorblind, http://www.amazon.com/exec/obidos/tg/detail/-/0375700730/ .

 

[Pangloss]

Gregory Cochran, a 'maverick' scientist, has published a thesis that proposes the Ashkenazi Jews both suffer particular forms of brain disease, and have heritable average higher intelligence than the broader population, due to inbreeding over many generations. The finding is apparently entirely based on statistical correlations, and no research has been done into the suggested causal connections, at the molecular level. It's created quite a stir - mainly due to the socio-political implications - and is interesting, at least. See http://www.economist.com/science/displaystory.cfm?story_id=4032638. I googled and found 355 references.

 

[arthwollipot]

Dawkins' The Selfish Gene has a very good explanation of this, but I don't have my copy with me so I can't elaborate.