Recently, mysterious topic has appeared in front of biologists, and that is Dark DNA. Dark DNA is defined as the large regions of DNA that are missing from a genome assembly. The genes are hidden but present as the mRNAs corresponding to these genes can be identified.
Adam Greff and his colleagues were researching sand rats (Psammomys obesus) to understand why this animal is susceptible to type-2 diabetes. They wanted to study the PDX1 gene (Pancreatic & Duodenal Homeobox 1) that controls Insulin secretion but found it missing with 87 other genes surrounding it. Some of these, including PDX1 genes, are necessary for survival. The genes are present but somewhere hidden. These genes are referred to as Dark DNA, similar to dark matter. Dark DNA has also been detected in birds previously- 275 genes were found to be missing!
The DNA sequence of these genes has high GC content regions. These GC –rich arrangements create problems for advanced DNA sequence technologies to detect rather than missing. Actually, the GC -rich content regions are the results of an excessive amount of mutation. But hotspot of higher mutation (genes in that location have a great chance of mutating others) could bias the direction of evolution, meaning natural selection may not be the sole driving force. It can be possible that mutations have taken place so quickly that natural selection cannot detect and remove anything in DNA. This mysterious topic is pushing scientists to rethink evolution!
Head of Daily Science Project, Bio Daily
Genetic Engineering & Biotechnology
Jagannath University, Dhaka-1100