Humans have come into existence after millions of years of conflict between genes. Some genes mutated while in some other the mutation was repressed
Sophie Salama, a research associate at the University of California, Santa Cruz, Genomics Institute, where researchers are studying the complex processes of human evolution, said, “We have basically the same 20,000 protein-coding genes as a frog, yet our genome is much more complicated, with more layers of gene regulation.”
How did humans and primates evolve and form complex genetic and cellular processes than frogs? The answer to this question could lie in the theory of an evolutionary arms race that has occurred between elements of the genome throughout history.
A recent study which appeared in the journal Nature reveals that there has always been a conflict among mobile DNA sequences also known as retrotransposons or “jumping genes”. These genes as the name suggests can jump from one part of the Genome to another to create or reverse a mutation. Now genes have also been evolved to control these mutations, genes which will produce proteins which can halt jumping gene activity. Researchers from UCSC have not only identified these repressor genes but have also discovered that they have evolved to play a vital role in the cellular processes.
The jumping genes constitute nearly 42% of the human genome. DNA transposons constitute around two to three percent. They are supposed to be leftovers of ancient viruses that inserted their genes into the genome long before humans evolved. Since jumper genes had hardly any use, the natural evolutionary process created the repressor genes which produced proteins to disrupt their activities. These repressor genes belong to a separate class of proteins which is known as “KRAB zinc finger proteins.” 400 genes constitute these DNA-binding proteins which are arranged in clusters in the human genome and 170 genes have appeared since primates split from other mammals.
The study reveals that the repressor proteins increased in number after a surge in jumping gene activity. The repression of the jumping gene could have caused other genomic effect and this must have been a part of the evolutionary process.
Salama said in a press release “The way this type of repressor works, part of it binds to a specific DNA sequence and part of it binds other proteins to recruit a whole complex of proteins that creates a repressive landscape in the genome. This affects other nearby genes, so now you have a potential new layer of regulation available for further evolution.”