The difference between Danny DeVito and Dolph Lundgren is given only by genes. So far, only two of these genes have been known. But three recent researches published in the journal "Nature Genetics" have augmented our knowledge on the issue, discovering dozens of new genes involved in this.

Height is a genetic trait, and what you got from your mother or father explains why you are shorter or higher than others. Forensics may one day detect the height of a criminal based on DNA probes. But if mutations causing dwarfism or gigantism are easier to detect, genes controlling normal stature have proven difficult to identify.

A new technique named genome-wide association manages to scan more rapidly the genome of an individual for DNA variations connected to common diseases. It has enabled the scientists to detect genes that make people more prone to diabetes and heart disease, but it has also discovered the first two DNA stretches connected to normal height variations.

The researchers analyzed the genome of 13,000 to 31,000 people. SNPs (single-nucleotide polymorphisms), minor changes of just one base in the DNA molecule, were looked for in association with taller or shorter than average stature.

The team led by Kári Stefánsson, a geneticist with deCODE Genetics in Reykjavik, Iceland, detected 27 new genes involved in height, and the other two teams, led by geneticist Timothy Frayling at Peninsula Medical School in Exeter, U.K., and Joel Hirschhorn, a geneticist at the Broad Institute in Cambridge, Massachusetts, detected 20 and 10 genes, respectively.

The researches have not been compared yet, thus some genes may have been found independently by two or all three teams. Most of the "tall" alleles (gene variants) were connected to a taller average height by 3.5 to 5 cm (1.4-2 in) compared to "short" alleles.

Some of these genes are involved in skeletal growth and development, while the way others control growth is a mystery, as they had been previously connected to genes involved in cancers or were encountered in DNA areas whose function is unknown. Even so, these newly found genes account for less than 4% of the normal height variation, thus much more "height" genes have to be discovered.

"The genome-wide association strategy may not be the best approach for identifying these remaining variations. The approach could overlook genes that affect height only when triggered by certain circumstances, such as a poor diet," said Justine Ellis, a geneticist at the University of Melbourne in Australia.