Tiny gene differences make us who we are
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Scientists have found more than 500 genes that account for variations across human populations including skin colour, height and vulnerability to disease, according to a new study.
By comparing millions of fragments of genetic code from individuals in four groups - from Nigeria, China, Japan and northwest Europe - researchers say that natural selection has played a key role in these differences.
The findings, which are published online ahead of print in the journal Nature Genetics, hold particular promise for understanding the genetic underpinning of certain diseases.
The researchers, led by Dr Lluis Quintana-Murci of France’s National Centre for Scientific Research pinpoints, for example, the tiny genetic variation in the CR1 gene that has made 85% of Africans highly resistant to malaria.
Most other populations in the world do not share this variant and are thus more susceptible to the mosquito-borne disease.
Other identified genetic variations - called single nucleotide polymorphisms or SNPs and pronounced ‘snips’ - could help explain why rates of diabetes, obesity and hypertension differ from one region to another.
Once the specific bit of genetic code responsible for a predisposition to a certain illness or condition has been identified, scientists can then set about trying to find a drug to treat it.
Variation matters
SNPs occur when one of the four chemical building blocks of DNA varies in a particular segment of DNA when compared with other members of the same species.
Some of these genetic mutations have happened through positive selection; they provide an advantage in the struggle to survive.
Being resistant to malaria is more useful in sub-Saharan Africa than in Norway, for example.
Others are driven by negative selection, the process by which genetic traits are forced out of a species because they impede survival.
Hair and eye colour
The study, based on the international HapMap catalogue of genetic variants within and among populations around the world, found SNPs that also account for differences in eye and hair colour.
“These genes played a role in adapting to our environment, and their mutation gave rise to certain advantages,” says Quintana-Murci.
“But the genes that explain the phenotypic differences between populations only represent a tiny part of our genome, confirming once again that the concept of ‘race’ from a genetic standpoint has been abolished,” he adds.
Genotype is the genetic blueprint contained in DNA, while phenotype is the individual organism brought into being based on the instructions contained in that DNA.
The study identified 582 genes that mutated through natural selection, probably between 10,000 and 60,000 years ago.
AFP
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