Junk DNA makes humans so different from primates

WASHINGTON - Repetitive stretches of “junk” DNA may partly explain why humans are so different from primates.

Medical researchers at the University of Iowa found that when a particular type junk DNA segment, known as an Alu element, is inserted into existing genes, they can alter the rate at which proteins are produced.

“Repetitive elements of the genome can provide a playground for the creation of new evolutionary characteristics,” said senior study author Yi Xing, assistant professor at Iowa’s Carver College of Medicine.

“By understanding how these elements function, we can learn more about genetic mechanisms that might contribute to uniquely human traits,” the journal Proceedings of the National Academy of Sciences reports.

Alu elements are a specific class of repetitive DNA that first appeared about 60 to 70 million years ago during primate evolution.

They are the most common form of mobile DNA in the human genome, and are able to transpose, or jump, to different positions in the genome sequence.

When they jump into regions of the genome containing existing genes, these elements can become new exons - pieces of messenger RNAs that carry the genetic information.

Although scientists have known that these Alu elements are an important source of new exons in the human genome, it has been more difficult to determine if these new exons are biologically important.

“Our new study says they do - they affect protein production by altering the efficiency with which messenger RNA is translated into protein,” said Xing.

Xing noted that in other circumstances, altering the rate of protein production can cause disease.