Can someone please explain: Why are non-coding regions of DNA more discriminating than coding regions? I forgot my textbook at school, and the internet is not providing me with a detailed enough explanation. Thanks.
Non-coding regions of DNA, also known as introns, are generally more discriminating than coding regions, or exons. This is because non-coding regions are less conserved across different organisms compared to coding regions.
To understand why non-coding regions are more discriminating, let's briefly go through the process of gene expression. When a gene is expressed, the DNA is transcribed into mRNA, which is then translated into a protein. In this process, introns are cut out of the mRNA molecule, and the exons are spliced together to form the final protein-coding sequence.
Coding regions, or exons, contain the instructions for the synthesis of proteins, which are essential for various cellular processes. These coding sequences often encode conserved domains of proteins, which are important for their structure and function. As a result, coding regions tend to be more conserved across different organisms since any changes in these regions could potentially disrupt protein function and lead to unfavorable consequences.
On the other hand, non-coding regions, or introns, do not code for protein sequences. While they were initially thought to be "junk DNA" with no function, it is now understood that introns play important roles in gene regulation, splicing mechanisms, and the evolution of genes. However, the specific sequences of introns can vary considerably between different organisms and even within the same species. This flexibility in non-coding regions allows for genetic variation and adaptation, as changes in introns are less likely to disrupt essential protein functions.
So, in summary, non-coding regions of DNA are more discriminating than coding regions because they are less conserved across different organisms. The flexibility in non-coding regions allows for genetic variation and adaptation without compromising essential protein functions.