The prevailing wisdom in genetics states that within a single organism the DNA in each cell is identical. The only exception to this rule is in the case of diseases such as cancer or other damaging genetic mutations that affect only a part of the organism.
A new study has found that this may be a false assumption. Researchers at Yale recently published a new study examining skin cells that have a very interesting attribute. Even though they have been taken from the same person the cells do not have identical genomes. These skin cells have been found to have a number of CNVs or copy number variations. A CNV occurs when a section of the DNA has been duplicated or deleted. This usually happens due to errors during the cell mitosis, or duplication, when a mother cell creates two daughter cells. If a CNV causes changes to vital genes then diseases or mutations can occur. It was long believed that the majority of cells had identical genomes and that only a handful of cells contained CNVs, and that most of the cells suffering this condition would cause disease and be killed off either by medical treatment or the body’s own immune system.
Genetic variations such as these are nothing new. Researchers already know that cells often mutate their DNA during mitosis. What they didn’t realize is how widespread it was. Upwards of thirty percent of the cells analyzed contained variations from the standard gene sequence.
The human body has a natural ability to detect and destroy mutated or cancerous cells before they become damaging. This study concludes that our bodies may allow for a mosaic of different genomes within our cells so long as the resulting cell is not damaging or cancerous and still functions properly.
This discovery was made when a group of Yale researchers were studying induced pluripotent stem cells or iPS. These stem cells are genetically engineered stem cells cultured from adult differentiated cells, and they may one day be used to repair damaged tissues throughout the body. In this case, the cells were cultured from skin cells taken from the underarms of several adults. While it is difficult to prove without culturing other types of differentiated cells, most of the cells in the body have this mosaic genome condition, the researchers assume. The team used whole genome sequencing to map the genetic sequence of the cells they were culturing and came up with differing genome maps. It took two years of growing and examining the cells to gather the results.
Researchers are now conducting new studies to see if these genetic variations occur in human brain tissue and the tissue of other animals.
The implications of this finding are serious–especially for forensic science, genetic screening and paternity testing kit. DNA may not be the fail-safe proof of identity that our current criminal justice system relies on so heavily. For example, in uk paternity testing, a DNA test analyzes the genome of a cell or group of cells with CNVs and compares it to a group of cells without CNVs, there may not be a paternity match.