DNA 'garbage' plays an important role

Scientists have long been puzzled about genetic material, called 'junk DNA', which takes up most of the genome but seems to lack certain functions. Why does nature force the genome to contain so much genetic material?

Researchers from Princeton University and Indiana University studied the genome of a pond living organism found that junk DNA is not really 'garbage'. They found that DNA sequences from regions previously thought to be "unnecessary genomes" actually have very important functions for organisms. They concluded that these genes promote the rearrangement of the entire gene needed for organism development.

The genes called transponsons in a single-celled protozoan Oxytricha produce proteins called transpossaes. During development, transposons affect the rearrangement of hundreds of thousands of DNA fragments. Then when not needed, the creature removed the transposases from its genetic material, reducing the genome's 'payload' by 5%.

Laura Landweber, professor of ecology and evolutionary biology at Princeton and an author of the study, said: 'Transponsons are actually central to cells. They combine genes together. ' The study is published in the May 15 issue of Science.

To prove that transposons actually have this combinational function, scientists neutralize thousands of these genes in some Oxytricha. Births with modified DNA cannot develop normally.

Other authors from Princeton's Department of Ecology and Evolutionary Biology include: Mariusz Nowacki and Brian Higgins; Genevieve Maquilan, and Estienne Swart graduate student. Post-doctoral researcher Thomas Doak of Indiana University is also involved in the study.

Princeton scientists are exploring the genome of the organism Oxytricha living in the pond. (Photo by Robert Hammersmith)

Landweber and other members of the research team are also investigating the origin and evolution of genes and genome sequencing, focusing primarily on Oxytricha because it undergoes large-scale gene recombination in the process. develope.

In his lab, Landweber studies the evolutionary origin of new genetics, such as Oxytricha. By combining molecular, evolutionary, synthetic and theoretical biology, Landweber and colleagues last year discovered a basic RNA mechanism for complex genome recombination.

Landweber said: 'Last year, we found instructions for how to bring the genome back together - information only comes from the form of RNA transmitted from parents to offspring and these RNAs provide template for recombination process. We are currently studying the actual mechanism involved in the process of cutting and joining large amounts of DNA. Transposons are responsible for this process'.

The term 'junk DNA' is used to indicate an area of ​​DNA that does not contain genetic information. Scientists began to discover that most of these junk DNA play an important role in controlling gene activity. However, no one knows the extent or scope of these DNA roles.

Instead, scientists sometimes call these regions 'selfish DNA' if they do not have a certain contribution to the development of the organism. Just like a computer virus multiplies itself. Selfish DNA also copies itself and passes from parents to children for the benefit of DNA alone. Current research shows that some selfish DNA transposons may play an important role for host organisms, thus becoming a permanent 'resident' of the genome.

References:
Mariusz Nowacki, Brian P. Higgins, Genevieve M. Maquilan, Estienne C. Swart, Thomas G. Doak, and Laura F. Landweber.A Role Function for Transposases in a Large Eukaryotic Genome.Science, 2009;324 (5929): 935 DOI: 10.1126 / science.1170023