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March 8, 2012

UVA-led team discovers new type of DNA outside chromosomes

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Researchers have discovered there are tens of thousands of previously unknown “ microDNAs ” outside the chromosomes in our cells. The groundbreaking research suggests that the generation of these microDNAs may create an unexpected genetic variation in tissue cells. That variation, in turn, may contribute to diseases that are suspected to have a genetic predisposition but for which there are no suspect genes, such as autism.

The research, led by Anindya Dutta, MD, PhD, Chairman of Biochemistry and Molecular Genetics at the University of Virginia School of Medicine , upends the commonly accepted notion that DNA is wholly contained within long chromosomes. Dutta’s team detected the short, circular microDNAs in both mouse and human cell lines, shedding new light on the makeup of mammalian DNA.

A link to autism?

The team determined that the generation of microDNAs leads to genetic variation within cells of the same tissue. Mistakes made as the DNA-copying machinery does its work prompt “micro-deletions” as the faulty microDNA is removed. This creates a mosaic of genetically varied cells within the same tissue, possibly leading to functional differences among them. Because of the nature of the process, there is an element of chance in which genes will be intact and which will suffer micro-deletions, Dutta says.

“The resulting genetic variation in our tissues could be important for diseases like schizophrenia or autism that have genetic predisposition but for which a single gene with a causative mutation has not yet been found,” he says.

A mystery in plants

In addition, the findings may help explain genetic behavior in plants that appears to defy the laws of genetics put forth by Gregor Mendel, the Austrian known as the father of genetics.

The new research findings have been published online today in the journal Science . The team includes researchers at UVA and the University of North Carolina at Chapel Hill.


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