Last Friday, Matthew Hahn, a biology professor from Indiana University presented his research on gene gain and loss in primates at the Dartmouth Medical School. Hahn’s research is concerned with explaining how the slight genomic difference between humans and chimpanzees translate into our remarkably differing morphologies. Hahn believes that this problem, known as the Wilson-King paradox, is not yet fully understood by geneticists because the appropriate research has been misdirected.
Research on the Wilson-King paradox has been primarily concerned with the ortholog, coding regions of the genome. Overlooked are the non-ortholog repeating portions of genetic codes. Hahn’s research has led him to believe that the solution to the Wilson-King paradox lies within a closer inspection of these genes. When genetic repeats are taken into consideration, the difference between humans and chimps is six times greater than when only active coding regions are studied.
This value was determined by examining gene movement in mammals. Genes, particularly those with repeats, tend to relocate within and between chromosomes over several generations. When such an event occurs, the genes themselves are sometimes altered. One copy of a gene repeat may break into multiple pieces, or place itself atop a different gene. This results in new genes being created as others are lost.
Over the millennia of evolution, Hahn has found that a significant number of genetic repeats have been gained by humans and lost in chimps through this type of movement. He has found that the rate for gene movement in primates is two to three times greater than in other mammals. The value among chimpanzees and humans is the greatest at .0039 of a gene every million years. Over a period of four to five million years of evolution, humans have gained 675 genes and chimpanzees have lost 740 genes. Furthermore, this means that there are 1,415 human genes that are not in chimpanzees.
Given these new values, Hahn believes a closer examination of genetic repeats is needed to resolve the Wilson-King paradox. While his study did not focus on the pathways of these repeats, Hahn believes his discovery will provide crucial direction to future investigations that do.