How many times have you been told you look just like your mom or dad? Well familial resemblance stems from inherited characteristics, or traits. The study of trait inheritance is genetics. DNA, central to genetics, allows for traits to be passed from parent to offspring and regulates the expression of such traits. So, one would think that all DNA codes for either a trait or a function. However, as scientists have gained a deeper understanding of DNA, they have found that in fact 98% of our DNA doesn’t code for anything. This type of DNA has been dubbed “dark DNA.”

At first, scientists thought that since dark DNA doesn’t code for anything, it shouldn’t serve a purpose either. However, as more studies have been conducted, scientists are finding that though dark DNA’s exact functions remain a mystery, it actually plays a significant role in genetics.

  One recent study has found that certain sequences of dark DNA, known as transposons, regulate the implantation of fertilized eggs into a mother’s uterus. Given its crucial role in embryonic development, dark DNA is key to the reproduction and survival of organisms.

  Other studies suggest that dark DNA may play a crucial role when it comes to genetic diseases. In a recent study with mice, scientists deleted a sequence of dark DNA and found that it resulted in abnormal brain function. Similarly, in a study with human patients affected by brain tumors, scientists found two mutations in the dark DNA in a tumor sample. Both of these studies show that dark DNA plays a role in gene expression within the brain and that mutations in such DNA can serve as a trigger for neurological diseases.

  Researchers have also found that dark DNA could contribute to evolution. Parts of dark DNA that repeat itself over and over again, are known as satellite DNA. In a study at MIT, scientists found that satellite DNA prevents incompatible species from creating viable offspring. The satellite DNA will scramble the chromosomes if such reproduction occurs. This would lead to the death of the hybrid offspring. So, since dark DNA prevents interspecies reproduction, it forces organisms to mate within their species. This eventually leads to evolution and speciation which is how new species are produced. Given this, scientists are looking at ways to manipulate satellite DNA to create new species and even revive endangered ones.

  Dark DNA may not explain why one has red hair or why people can’t seem to tell you and your brother apart but it does remain a promising area of study. And despite many recent findings and ongoing research, there still remains a lot of light that can be shed on dark DNA.