Dr Francis Collins, the scientist leading the Human Genome Project, says he expects important new gene sequences governing aspects of personality, such as intelligence and behaviour, to be known very shortly.
Dr Collins directs the US National Human Genome Research Institute
While the project to crack our DNA code has been targeted at understanding and eradicating disease, Dr Collins believes the project will provide significant insights into a broad range of heritable aspects.
"We haven't discovered most of those yet, but frankly, we should be prepared for an avalanche of that kind of information coming in the next two or three years," he told the BBC World Service's The Interview programme.
"On top of the Human Genome Project, which laid out the letters of the code in a 'reference DNA sequence' way, we now have a very good encyclopaedia of the variable parts.
"Researchers are using those in very powerful ways, to track down the specific genes involved in very complicated things - including intelligence," said the director of the US National Human Genome Research Institute.
Dr Collins stressed that understanding the genes governing behaviour was not the main focus of the Human Genome Project.
Instead, it remains firmly focussed on identifying the faulty genes responsible for disease, such as diabetes, heart disease, and cancer.
"We'll find those, too; but there's going to be a lot of behavioural studies involved, and they will yield up some pretty interesting discoveries," he said.
THE DNA MOLECULE
The double-stranded DNA molecule is held together by four chemical components called bases
Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G)
Groupings of these "letters" form the "code of life"; there are about 2.9 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes
Written in the DNA are about 20-25,000 genes which human cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies
"We will then have to figure out how to internalise that. Again, there is this risk that if we discover some of those variants, people will say, 'a-ha - that proves it really was just nature all along'.
"Then we'll forget about the nurture part - and that would be a terrible mistake."
Dr Collins warned that that a number of ethical questions would be raised by the discoveries, although he also stressed that it was not scientifically possible to engineer DNA, for example, to make people more intelligent.
"We may be able to discover variations that correlate with intelligence, but to actually utilise that, to tinker with the human gene pool, is ethically a very difficult and challenging topic," he said.
"Scientifically, it's not something we know how to do."
And Dr Collins said that even if it were possible to augment intelligence - for example with a pill to raise it - it would potentially create a great divide between "who has access and who does not".
"If this is a particular approach which is very expensive and only available to people with lots of resources, then what have you done? You've created a divide in an already divided world.
"That is a very dangerous and troubling outcome, which I think we should guard against."