Look into my DNA…

10 March 2009


Human eye


Looking around at families, it's obvious that certain characteristics, such as hair colour and eye colour, can be inherited.  But it's surprisingly difficult to tell from a DNA sequence exactly what characteristics a person might have.  But, according to a report in this week's edition of Current Biology, a group of scientists in the Netherlands have developed a way to tell what colour eyes a person will have, just from a sample of their DNA.

Although you may think eye colour in simple, it's actually what biologists call a "complex trait", which is determined by several different genes. Over the years, a number of these genes have been found, and it's a combination of certain variations of these that give us our eye colour.

Manfred Keyser and his team have analysed the DNA of more than 6,000 Dutch people, and linked variations in 8 eye colour genes to their actual eye colour. In fact, they started by looking at 37 gene variations, known as SNPs ("snips"), in the 8 genes, and narrowed it down to the 6 best SNPs in 6 genes that were most strongly linked to eye colour.  They found that testing these 6 SNPs could predict whether a person's eyes would be blue or brown with around 90 per cent accuracy.  For people with other colour eyes - like my own green peepers, they were about 75 per cent accurate.

For a start, this is an important proof-of-principle experiment - this is the first time that scientists have managed to show that a complex trait can be predicted with any kind of accuracy from DNA alone.  So if we can manage to do this for other complex traits, such as hair or skin colour, then it might be possible to draw up a basic profile of  criminal from DNA at a crime scene.

Of course, there's a lot still to be done. This study was only done in Dutch European people, so we need to find out if the results hold true across other populations, although it's likely that they will. And, of course, it's always possible to pop in some coloured contact lenses to evade the police.  But it would also be useful for drawing up a profile of murder victims or other deceased people who are too decomposed to keep identifying features.








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