The human genome is as ginormous as it is complex. The more we try to unravel it, the more novelties it presents.
When the 13-year-long effort to sequence the human genome concluded in 2003, almost 90% of the human genome was sequenced. It was as if we knew *almost* everything about it.
Certain minor gaps in the study were thought to constitute ‘Junk DNA,’ which didn’t appear to code anything important. But now, a new study has presented an ‘evolved’ discovery.
It seems that all the ‘Junk DNA’ wasn’t really trash after all, but a treasure trove which has given rise to hundreds of essential microprotein-encoding tiny genes in our genome. Some of these are as recent as the human-chimpanzee split, showing how humans have continued to evolve and develop new functional genes over the years.
‘Self-made’ tiny genes which possibly perform vital functions
Researchers from Biomedical Sciences Research Centre (BSRC Flemming) in Greece and Ireland’s Trinity College Dublin have identified 155 genes in the human genome which interestingly emerged from scratch, building upon the tiny, non-coding sections of DNA.
This is surprising given these non-coding ‘junk’ sections do not have the instructions our bodies need to build functional molecules.
There are different ways through which our new genes are birthed. Typically, it occurs via duplication, where our genetic machinery accidentally hits the copy button, giving rise to replicas of pre-existing genes, which then evolve different functions over time.
But unlike their counterparts, these newly discovered genes have no ancestors. They have appeared de novo, meaning entirely from scratch.
Road to the discovery of 155 new microgenes
To unveil these hidden gems in our genome, the study team analysed the human reference genome and compared it with those of 99 vertebrate species, tracking their evolution over millions of years.
The ancestral tree reveals that some of these genes appeared as early as when the earliest mammals lived, and two of these genes have emerged quite recently since humans and chimpanzees branched off from Gorillas. Of these latter two, one even has a possible function in constructing the tissue of the human heart!
This is striking evidence of the fact that humans have continued to evolve despite parting ways with the primate cousins.
Further comparative analysis found that 44 of the 155 new genes are associated with growth defects, while three have links with diseases such as muscular dystrophy, retinitis pigmentosa and Alazami syndrome.
One reason why these microgenes have been overlooked for so long is because their size makes them difficult to find. Even the microproteins they produce are so tiny that analysing them is super tough.
So far, scientists have determined the positions where the genes are expressed, but their role and impact on human health still need to be clarified.
“If we’re right in what we think we have here, there’s a lot more functionally relevant stuff hidden in the human genome,” says McLysaght.
The findings of this study have been published in the journal Cell Reports and can be accessed here.
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