In the 1970's scientists discovered that certain cells can shuffle and edit DNA which is known as somatic recombination. Some of these cells include immune cells and B cells. Scientists have also seen hints that it could also be occuring in our brains in neurons. Neurons can differ dramatically from one another with some having more DNA than neighboring cells. Neuroscientist Jerold Chun and his colleagues aim to find definite evidence of somatic recombination in the brain. They conducted research on donated brains of healthy elderly people and patients who had non-inherited Alzheimer's disease. They tested to see if the cells had different versions of the gene for the amyloid precursor protein (APP), the source of the plaques in brains of those with Alzheimer's. They wanted to do it on APP because other studies have shown that neurons of patients with Alzheimer's can have extra copies of the gene which could possibly come from somatic recombination. The researchers were able to identify that neurons seem to carry thousands of APP gene variants. From the study they also discovered that neurons from the Alzheimer patients had about six times as many varieties of the APP gene as did the cells from the healthy people. His team thinks that reshuffling depends on an enzyme called reverse transcriptase that makes DNA copies from RNA molecules. They believe that a new variant could arise when the enzyme duplicates the APP gene and slips it back into the genome. This can create a sloppy copy that may not match the original and code for a different variant of APP. If more studies occur that confirm what they think then we can block the enzyme like treatment for HIV and work against Alzheimer's disease.