Breakthrough In Human Genetics

Many readers have submitted this story about a breakthrough in our understanding of human DNA: in particular, how much variation can exist between peoples' genes and how genes are involved with certain diseases. "One person's DNA code can be as much as 10 percent different from another's, researchers said on Wednesday in a finding that questions the idea that everyone on Earth is 99.9 percent identical genetically. They said their new version of the human genetic map, or 'book of life,' fills in many missing pages and chapters to explain how genes are involved in common diseases. The Human Genome Project mapped the billions of letters that make up the human genetic code. Scientists later refined the map by looking for single variations called SNPs or single nucleotide polymorphisms. The CNV map gives researchers a different way to look for genes linked to diseases by identifying gains, losses, and alterations in the genome."

Comments

Good Science meet bad math

[DrKyle]

Looking at the writeup from Nature. They clearly state that these results point to maybe a 0.5% difference among individuals, or 99.5% identical. That's 20X less variation than this crap article would have you believe. The actual research deals with CNV's = copy number variants. So for a given stretch of DNA, different people in a population might have that region duplicated or triplicated which does not really allow them to make anything different, but it might alter the levels of expression of those genes. As this DNA is found in multiple copies it had largely been believed to have a low number of genes, as is the case of most highly repeated DNA, but the researchers have evidence that these repeated domains do contain a large number of unique genes. In a short summary/analogy:
Some people are 8 feet tall.
Some people are 4 feet tall.
Therefore, people vary in height by 200%.

It's obvious to see the failed logic in that case, that's the same thing here, just because 10% might potentially be variable, that doesn't mean any single person even exists at each extreme.

Re:Actually

[John Newman]

It depends on what, exactly, you are comparing. If you pick out a human gene and its chimp counterpart, and line up the sequenes, you find they are about 99.8% identical at the nucleotide level (and often 100% identical when you look at the encoded amino acids). These regions are presumably under selective pressure. If you do the same for corresponding non-gene sequences, ones which are not under selective pressure, you find they are 98.6% identical. However, now that the two genomes are essentially complete, we know that there are some large-scale duplication and deletion events, as well as variations in mobile elements, that make the overall identity between the two genomes somewhat less than the 98-99% identity between homolgous sequenes. So 95%, 98.6%, or 99.8% - all are correct answers in the correct context.

(IIABioinformaticist)

Re:Actually

[superyooser]

Another article covering this discovery puts the difference at 96%.

Another implication of the finding is that we are more different to our closest living relative, the chimpanzee, than previously assumed from earlier studies. Instead of being 99 per cent similar, we are more likely to be about 96 per cent similar.

Better Article

[BrickM]

http://news.independent.co.uk/world/science_techno logy/article2007490.ece

This piece gets a few of the key facts correct where reuters went wrong, such as the already-mentioned "10% vs 10x" difference between individuals. It's a great read!