Another advance thanks to the human genome project

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The completion of the human genome project has opened up new possibilities in the study of genes and behaviour.

Scientists have already identified genes, or more accurately variations in genes, that can be linked with behaviours as diverse as anxiety, depression, hostility, aggression, sex drive, addiction and even criminality.

Just as genes are responsible for providing the digital recipe for making the blood, flesh and bone of the body, they are also responsible for the cells and nerve fibres that make up the brain and central nervous system.

It is little wonder, say scientists, that genetic inheritance deals the cards that predispose someone to mental disorders such as depression or risk-taking behaviour such as gambling or alcoholism.

Of course, the environment - in this case upbringing and education - plays a critical role in the psychological development of any child. But scientists have shown that both nature and nurture can interact in a complex manner to shape the psychological and emotional identity of a person.

One pioneering study, for instance, showed that children who suffer serious maltreatment and are born with a particular variation in a gene for a brain enzyme are at significantly higher risk of developing serious anti-social behaviour compared with children without the gene - even if those children have been similarly abused.

This study showed that a person's genetic make-up up can influence their susceptibility to a particularly traumatic episode in their early upbringing. Other children may be fortunate in having a genetic make-up that makes them resistant to such trauma.