On rare occasions, one egg that has already been fertilized will split into two. When this occurs, identical twins are born and share the same genetic makeup. There is also the occurrence of “fraternal twins.” These sets of twins come from two different eggs and are fertilized by two different specimens of sperm. Because identical twins share the same DNA, the results would largely be the same if they were analyzed in a genetic lineage test. In contrast, the outcome for fraternal twins would be very different.
Twins with Different Health Issues
Even though identical twins share the same genes, they don’t automatically have the same health issues. Scientists at the University of Michigan Medical School studied a sample of identical twins to learn more about the autoimmune disorder rheumatoid arthritis.
In a study done at the University of Michigan Medical School, researchers learned that there are three different genes that cause people to contract rheumatoid arthritis. They also discovered that non-genetic factors were largely responsible for the over-expression of these genes. In their sample of eleven pairs of twins, only one had the disease, and the three afore-mentioned genes were over-expressed. How this can occur in just one twin and not the other is a question that these medical professionals are extremely interested in answering. A peek into what the reason may be comes from scientific discoveries that are now being used to identify suspects in criminal cases.
Can Police Forensics Experts Tell Identical Twins Apart?
In the past, it was impossible for police forensics experts to definitively say that one person committed a crime and not the other, but this is no longer the case. In actuality, there are genetic differences between identical twins, as in every individual and forensics experts can discern them.
The DNA of twins developing in the womb is exactly the same. However, environment plays a large role in the genetic makeup of identical twins and all individuals. As people travel throughout their lives, chemical marks called “epigenetic markers” determine which genes to turn on and which ones to leave dormant. These markers come and go according to people’s life experiences, and these will be different for each individual. Also, DNA is always in the process of mutating, and the same mutations are not likely to occur in some people.
Therefore, even though identical twins share the exact same genetic linage and DNA at birth, because of environmental factors, epigenetic markers and gene mutations occurring throughout living their lives, identical twins can experience contrasting life experiences due to health and constantly mutating genes. Also, even though they make look indistinguishable from one another, a simple DNA test could decipher the guilty from the innocent.