An international team of scientists said recently that the largest brain study of its kind had found a gene linked to intelligence, a small piece in the puzzle as to why some people are smarter than others.

A variant of this gene “can tilt the scales in favour of a higher intelligence,” study leader Paul Thompson told AFP, stressing though that genetic blessings were not the only factor in brainpower.

Searching for a genetic explanation for brain disease, the scientists stumbled upon a minute variant in a gene called HMGA2 among people who had larger brains and scored higher on standardised IQ tests.

Thompson dubbed it “an intelligence gene” and said it was likely that many more such genes were yet to be discovered.

The variant occurs on HMGA2 where there is just a single change in the permutation of the four "letters" of the genetic code.

DNA, the blueprint for life, comprises four basic chemicals called A (for adenine), C (cytosine), T (thymine) and G (guanine), strung together in different combinations along a double helix.

In this case, the researchers found that people with a double ‘C' and no ‘T' in a specific section of the HMGA2 gene had bigger brains on average.

The discovery came in a study of brain scans and DNA samples from more than 20,000 people from North America, Europe and Australia, of European ancestry.

People who received two Cs from their parents, a quarter of the population, scored on average 1.3 points higher than the next group — half of the population with only one C in this section of the gene.

The last quarter of people, with no Cs, scored another 1.3 points lower.

“The effect is small,” said Thompson, but “would be noticeable on a (IQ) test.”

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