How did human genome evolve into a complex regulatory networks that control the activity of genes in every single cell of our bodies? Note that, according to the Smithsonian magazine, there are 37.2 trillion cells in your body. Well, scientists at the University of California, Santa Cruz have discovered that an evolutionary race between rival elements in the genomes of primates triggered the evolution of complex regulatory systems.
Jumping genes…and the race to prevent them
The race was between jumping genes or “retrotransposons” and genes that have evolved over time to control them. For the first time, scientists led by Frank Jacobs of the University of California, have identified genes that produce repressor proteins. These repressor proteins are capable of deactivating a specific type of jumping genes.
Scientists were also successful at tracing the evolution of repressor genes in primates. Sofie Salama, co-author of the study, said that, in primate genomes, there were repeated episodes over time when mutations in jumping genes helped them escape repressor proteins, which in turn prompted evolution of new repressor proteins.
Early repressor genes now play different roles in human genomes
It indicates that repressor genes that evolved over time to deactivate jumping genes have come to play other roles in human genomes. Salama said our genomes have the “same 20,000 protein-coding genes as a frog.” Still, human genome is a lot more complicated, with many more layers of gene regulation. Researchers believe jumping genes are just remnants of viruses that attacked ancient animals and inserted their genes into the animal genome even before humans evolved.
Today, these jumping genes or retrotransposons can replicate only within the genome. A jumping gene can disrupt the activity of normal genes and cause some serious diseases depending on where in the genome the new copy gets inserted. In most cases, the effect is neutral. In very rare instances, the jumping event could be advantageous. But there is a high probability of harmful effects. Therefore, natural selection favors the evolution of mechanisms (such as repressor proteins) that can prevent jumping events.
Findings of the study appeared in the journal Nature.