They may look alike, talk alike and walk alike, but twins can be very, very different when it comes to their genetic makeup, revealing why one identical twin may develop a hereditary disease, but not the other.
In a recent study of 19 pairs of identical twins, scientists from Alabama, The Netherlands and Sweden collaborated and discovered significant DNA differences within the copy number variation (CNV). Translation from science speak… CNV occurs when a set of coding letters in DNA are missing, or when extra copies of segments of DNA are produced.
"The presumption has always been that identical twins are identical down to their DNA," said Carl Bruder, Ph.D. and Jan Dumanski, Ph.D., of the University of Alabama's Department of Genetics and the study's lead authors. "That's mostly true, but our findings suggest that there are small, subtle differences due to CNV. Those differences may point the way to better understanding of genetic diseases when we study a pair of twins where one twin has a disorder and the other does not."
In the past, when one twin developed a particular disease -- Parkinson's, for example -- while the other did not, it was thought that environmental factors were the likely culprits, not genetics. With their new knowledge, Bruder and Dumanski indicate that CNV should be efficiently studied in identical twins.
"Changes in CNV may tell us if a missing gene, or multiple copies of a gene, are implicated in the onset of disease," Bruder said. "If twin A develops Parkinson's and twin B does not, the region of their genome where they show differences is a target for further investigation to discover the basic genetic underpinnings of the disease."
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