Gene duplication identified as part of human evolution

A recent study has shed some light into at least one of the genetic mutations that may be responsible for a critical part of human evolution.

What amounts to a copying error could have caused some of the features of the human brain that distinguish us from our closest primate relatives.

Of course we know that evolution occurs via genetic mutation. When cells divide in an organism, the entire genome is copied. During this process, mutations can occur when parts of the genome are either skipped or duplicated accidentally.

In cases of gene duplication, an extra copy of a gene is created and since it is not necessary to the organism, it can then be changed in future copies either gaining more mutations or losing parts. Over many generations and divisions, a new feature can evolve.

Researchers from the Scripps Research Institute in La Jolla California scanned the human genome for duplications. They found approximately 30 genes that have persisted as selective duplications - many of which seem to be involved in brain development.

Not only did they find these examples of selective duplication within the human genome, but they appear to be some of our most recent genetic changes.

The recent study published in the journal Cell in May examined the gene SRGAP2, which scientists believe has been duplicated at least twice during the course of human evolution, 3.5 and 2.5 million years ago.

In this study, the second duplication of this gene (an incomplete duplication) was added to the mouse genome with interesting results. When added, the gene seemed to increase the speed of brain cell migration during brain development. The cells with this duplication also had more 'spines' on them to connect to other brain cells, which made them look more like human brain cells.

Looking back over the evolutionary trail of humans, this second duplication of SRGAP2 appears to have come into being right around the time when the brains of our ancestors began to expand, a time when big changes in cognitive abilities probably emerged and dramatically set us a part from many other species.

All of this is certainly interesting as it sheds more light onto how our genetic make-up likely developed over time and resulted in the incredibly specialized and efficient modern human brain.

More research will continue to uncover the selective purpose behind these and other features within the human genome and will undoubtedly shape the future of human medicine.


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