IN A remarkable piece of detective work, genetics researchers at Trinity College Dublin have made the first discovery of genes that are completely unique to humans.
Most of our genes are duplicates or rearrangements of genes from evolutionary ancestors, so the find may help to explain what exactly it is that makes us human.
Research leader Dr Aoife McLysaght and Dr David G Knowles, of TCD’s Smurfit Institute of Genetics, conducted comparisons of human, ape and monkey DNA.
They identified three genes that are found only in humans, reporting their findings this morning in the leading journal, Genome Research. They predict that there may be as many as 18 such genes hidden in our DNA, after conducting research funded by a Science Foundation Ireland President of Ireland Young Researcher Award.
Equally startling is that these genes were discovered in what had been considered “junk” DNA, non-functioning strings of repetitive DNA that do not seem to do anything.
Genes are the working parts of our genetic blueprint. They produce proteins and enzymes needed by the body to make cells function.
Scientists have long assumed new genes could only evolve from duplicated or rearranged versions of preexisting genes, passed on by our ancestors, Dr McLysaght said. But then scientists began to discover a very few novel genes in species such as flies and yeasts that arose from apparently inactive junk DNA.
“This is the first ever discovery of novel human-specific protein coding genes,” said Dr McLysaght. “They are found in humans and nowhere else.”
Primates including gorillas, gibbons, macaques, chimps and orang-utans all carry very similar lengths of DNA, evidence that apes, monkeys and humans share a common ancestor. Yet this junk mutated in humans to produce uniquely human genes, she said. It was not enough for the researchers simply to discover suspected genes, they also had to prove the genes produced proteins. This they did, also showing that the same DNA strings in other primates did nothing. “We don’t know what these genes do so we can only speculate on whether they deliver human-specific attributes, higher level functions like language and social skills,” she added. “Genes that are human- specific are likely to be important to these.”
Efforts are now under way to identify what these genes are for, how the proteins they produce are used in the body and where. “We are trying to figure out what these genes do.”
She acknowledged that her estimate of just 18 human-specific genes in the entire two billion step human genome seems very small. Once they became active, however, the proteins produced would have had a profound effect.
