PROVIDENCE, R.I. [Brown University] -- When cells reproduce, their DNA is copied and mistakes are made. These mistakes, or mutations, range from changes in a single letter of the DNA sequence to drastic deletions, duplications or rearrangements of genetic code. The result is genomic variation, which is responsible for major distinctions between species think flippers, legs and wings as well as subtle differences within a species, such as eye color or blood type.
Scientists at the University of California, San Diego (UCSD) and Brown University have devised a new method for detecting one source of genomic variation, the "microinversion." These mutations occur when short DNA sequences anywhere from a few dozen to a few thousand base pairs of genetic code break away from the chromosome and then reattach in the reverse direction. The result: A string of code that ought to read "ATTAGCCG" reads "GCCGATTA" instead. Microinversions have been linked to infertility and a rare form of muscular dystrophy.
Distinguishing microinversions from other types of mutations can be tricky, particularly when comparing DNA sequences of distantly related species. This task is now more reliable due to a new software program called InvChecker. Created by computer scientists at UCSD and Brown, and detailed online in the Proceedings of the National Academy of Sciences, the system allows scientists to compare the DNA sequences of different species and identify regions that include the same microinversions.
The software draws on the idea that microinversions are generally preserved during evolution and are much easier to spot when comparing three or more species. For example, if scientists see a microinversion when comparing the human and chimpanzee genomes, this similarity could be the result of chance. But if they see the same reversed sequence of DNA in the rat and rabbit genomes, it is more likely that the mutation is, indeed, shared.