Posted: Tue 18 Nov 2008 15:53 Post subject: Can autosomal tests be used to make predictions of physical
Are autosomal tests utterly useless for making predictions about physical appearance? If the answer is yes, why are forensics using them to infer the "race" of a criminal?
Joined: 07 Feb 2007 {Posts: 1829 } Location: Lookin DC Metro, Feelin Geneva
Posted: Tue 18 Nov 2008 15:55 Post subject:
You mean as in hair color, eye color, skin coloring (to a certain %) The answer is yes if they are testing for those genes and you kno what the genes mean...what variation, etc.
If you are asking if they can produce a computer generated print out of what people would look like as a child or adult...then the answer is NO.
We are not nearly that advanced, we barely know what all the genes do and how they interact with other proteins.
Mapping the genome, identifying genes and knowing their function are two different things.
[quote="Dragon Horse"]You mean as in hair color, eye color, skin coloring (to a certain %) The answer is yes if they are testing for those genes and you kno what the genes mean...what variation, etc.
Yes that is what I mean. Is there a cut-off for the percentages needed to predict skin tone, hair color and eye color for example?
Posted: Tue 18 Nov 2008 16:30 Post subject: Re: Can autosomal tests be used to make predictions of physical
Sadie wrote:
Are autosomal tests utterly useless for making predictions about physical appearance? If the answer is yes, why are forensics using them to infer the "race" of a criminal?
As DH said, autosomal tests for ancestry-informative admixture mapping (how many of your ancestors came from which colonial population) do not measure external features. They measure only non-functional variations within your DNA that happen to differ between the different colonial populations.
I suppose that in extreme cases you could use autosomal tests to predict which "race" a person would be assigned to by U.S. society. If the overwhelming majority of a person's ancestors came from Europe, then it would be a reasonably safe bet that he/she would look White to most Americans. And if almost all of a person's autosomal markers came from Africa, then I would bet that most Americans would see the person as Black.
But the problem is that many people are mixed to some extent. A person of, say, 70-30 Euro-Afro admixture could look like anything. Also, "Hispanics" are a distinct "race" according to federal EEOC regulations. Hence, forensics must distinguish between Hispanics and other mixed people. They do it based upon the person's culture or language.
Finally, I would like to know where you got the information that forensics are using autosomal DNA to infer the "race" of a criminal. To my knowledge, autosomal DNA tests (like avowed self-identity) have been ruled irrelevant and cannot be introduced in evidence in racial-classification cases. There was one case of a Louisiana serial killer whose autosomal DNA was so overwhelmingly African, that the DNA lab told police they should be looking for someone who looked African, not European. Although this suggestion allowed the police to find the killer, the autosomal results were not allowed to be introduced as evidence.
Forensic anthropologists do use a series of markers for identification, but these are unrelated to the Afro-Euro-NA markers used for ancestry-informative admixture mapping.
Mr. Sweet thank you for very much for the information. The racial profiling I was referring to was indeed that case(Derrick Todd Lee) but I didn't know this info was inadmissible as evidence. And also, I believed since it was done once and was proved successful, that it was still being practiced.
Joined: 07 Feb 2007 {Posts: 1829 } Location: Lookin DC Metro, Feelin Geneva
Posted: Tue 18 Nov 2008 21:07 Post subject:
[quote="Sadie"]
Dragon Horse wrote:
You mean as in hair color, eye color, skin coloring (to a certain %) The answer is yes if they are testing for those genes and you kno what the genes mean...what variation, etc.
Yes that is what I mean. Is there a cut-off for the percentages needed to predict skin tone, hair color and eye color for example?
I can give you an example with skin color.
They can test genetically if a person has a light skin gene that is more prevalent in Asians or more prevalent in Europeans.
Quote:
Polymorphisms in 2 genes, ASIP and OCA2, may play a shared role in shaping light and dark pigmentation across the globe, whereas SLC24A5, MATP, and TYR have a predominant role in the evolution of light skin in Europeans but not in East Asians. These findings support a case for the recent convergent evolution of a lighter pigmentation phenotype in Europeans and East Asians.
That being said, that does not necessarily make one European or East Asian...it just means they are more likely to be, obviously in Eastern Europe and Central Asia that would be a useless indicator and still tell you nothing about appearance per se.
Why? Well there are several genes involved in skin coloring....I believe because there is no gene that is 100% determinant in skin coloring. I believe, I have to look it up, they found a gene in Europeans that is about 60% at best...so while this makes a person lighter, how light depends on the other genes.
Here is an example of how complicated this is:
Quote:
Harding found that there were zero differences among the Africans for the amino acid sequences in their receptor proteins, so the skin of each individual from Africa was dark. In contrast, among certain (European) non-African individuals, there were 18 different amino acid sites in which the receptor proteins differed, and each amino acid that differed from the African receptor protein resulted in skin lighter than the skin of the African (and other equatorial) individuals. Nonetheless, the variations in the 261 silent sites in the MC1R were similar between the Africans and non-Africans, so the basic mutation rates among the Africans and non-Africans were the same. Also, close examination of the haplotype variation among the non-Europeans (including East Asians) suggested that, among most non-European non-Africans, the most common variants were in the silent mutation positions (Harding et al 2000 p 1355). Thus, at least at this locus, most non-Europeans share the ancestral function. The fact that relatively light skinned east Asians varied little genetically from dark skinned Africans at this locus supports the fact that skin color is a complex trait determined by several genes. Thus light skin among east Asians occurs by way of a different genetic mechanism than that among Europeans.
Even in Europe, this central light skin gene is not fixed in every population.
This is why you have some "whites" born significantly darker than others, when they come from the same population. The "black Irish", the very pale Russians and the fairly dark Mediterranean ones, often from the same family, etc.
So you can see it is not an easy thing to judge appearance from genes, because genes usually do not work in isolation.
I didn't even get into skeletal shape, height, etc. Imagine how complex that is.
In the future it might be possible, with some very advanced computer technology to make a rough sketch of what someone will look like by just looking at their genetic material, but we are a long long way off from that.
As I said, right now, you might be able to tell if someone has blue eyes as blue is recessive and we know the gene, so if they have two copies of it, they must have blue eyes...but there are "black people" in America with blue eyes or have blue eyed genes.
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