Human-Specific Traits: Loss of Regulatory DNA
One strategy for understanding unique human characteristics is to look for genetic differences between humans and our animal relatives. Though most of our DNA is non-coding, at least some of this so-called "junk DNA" performs a regulatory function, turning coding genes on and off. While some of human uniqueness can be attributed to gene mutations, the non-coding DNA also plays a role; and the DNA that has been lost in the transition is turning out to be surprisingly important. One group of researchers identified chunks of DNA that were lost in humans but retained in chimpanzees. Almost all of the 501 deletions they found were in non-coding DNA. The first step in determining the effects of these deletions is to look at the functions of the genes they are closest to. Not surprisingly, large numbers of deletions were found near genes involved in neural function, particularly those that suppress cell proliferation or migration; evidence suggested that these deletions account for enhanced growth in several areas of the human brain.