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Phenotypes such as; skin color, eye color, nose shape, lip size, limb proportions, and skull shape.

Im trying to find a source for this quote.

"If you ask what percentage of your genes is reflected in your external appearance, the basis by which we talk about race, the answer seems to be in the range of .01 percent," said Dr.

Harold P. Freeman" From - http://astro.temple.edu/~ruby/opp/racesnyt.html

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  • $\begingroup$ That source is outdated, but I think the answer is 1) yes, it is possible and 2) the number of genes that make humans appear different is indeed exceedingly small. Consider that (if I'm not mistaken) a tiny soil-dwelling worm (the nematoad C. elegans) has about 20,000 genes, and at least 40% of them have human counterparts. Look at dogs: a chihuahua and a great dane have the same genes. How hard can it be to believe that quote? $\endgroup$ – anongoodnurse Jan 22 '15 at 4:46
  • $\begingroup$ Its not hard I just need a peer reviewed source. $\endgroup$ – Deondre Patrick Jan 23 '15 at 3:43
  • $\begingroup$ I tried and couldn't find any. $\endgroup$ – Deondre Patrick Jan 23 '15 at 3:46
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Height

This is just a single example, but "height" has received a lot of GWAS (genome-wide association study) attention, and last year the GIANT consortium published results of an analysis on 250,000 people looking at the genetic influences of height [1].

Using just 2,000 genetic variants they could statistically account for 20% of the phenotypic variation in height. Using 9,500 genetic variants this rose to 29%.

What this emphasises is that common traits (such as height) are highly polygenic; there is no "height gene" that controls it - instead it is the combination of many small-effect variants that cumulatively give rise to an individuals final phenotype (height, in this case).

Pigmentation

Pigmentation (of eyes, skin and hair) on the other hand is not nearly as polygenic. A 2013 review [2] discussed the known genetic variation for these traits. Prediction of eye colour using genetics, for instance, requires only six genetic variants "to be suitable to predict blue, intermediate, and brown colors with an overall accuracy of 0.91, 0.72, and 0.93, respectively".

So in contrast to height where even with 9,500 variants measured you would still only have 29% accuracy, you can be 91% sure that someone will have blue eyes if you know the individuals genotype at only 6 positions.

So in short the quote you reference is incorrect - we can predict many common traits with reasonable accuracy - although for some phenotypes the individual predictive capability of a specific genotype may be around 0.01% (e.g. some of the height variants).


  1. Wood, A. R. et al. (2014) Defining the role of common variation in the genomic and biological architecture of adult human height. Nat Genet 46, 1173-1186, doi:10.1038/ng.3097
  2. Liu, F., Wen, B. & Kayser, M. (2013) Colorful DNA polymorphisms in humans. Seminars in Cell & Developmental Biology 24, 562-575
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