It’s not enough that DNA is a language but now it has proofreaders?:
On the DNA assembly line, two proofreading proteins work together as an emergency stop button to prevent replication errors. New research from North Carolina State University and the University of North Carolina at Chapel Hill shows how these proteins — MutL and MutS — prevent DNA replication errors by creating an immobile structure that calls more proteins to the site to repair the error. This structure could also prevent the mismatched region from being “packed” back into the cell during division.
When a cell prepares to divide, the DNA splits, with the double helix “unzipping” into two separate backbones. New nucleotides — adenine, cytosine, guanine or thymine — are filled into the gaps on the other side of the backbone, pairing with their counterparts (adenine with thymine and cytosine with guanine) and replicating the DNA to make a copy for both the old and the new cells. The nucleotides are a correct match most of the time, but occasionally — about one time in 10 million — there is a mismatch.
“Although mismatches are rare, the human genome contains approximately six billion nucleotides in every cell, resulting in approximately 600 errors per cell, and the human body consists of more than 37 trillion cells,” says Dorothy Erie, chemistry professor at UNC-Chapel Hill, member of UNC’s Lineberger Comprehensive Cancer Center and co-corresponding author of the work. “Consequently, if these errors go unchecked they can result in a vast array of mutations, which in turn can result in a variety of cancers, collectively known as Lynch Syndrome.”
A pair of proteins known as MutS and MutL work together to initiate repair of these mismatches. MutS slides along the newly created side of the DNA strand after it’s replicated, proofreading it. When it finds a mismatch, it locks into place at the site of the error and recruits MutL to come and join it. MutL marks the newly formed DNA strand as defective and signals a different protein to gobble up the portion of the DNA containing the error. Then the nucleotide matching starts over, filling the gap again. The entire process reduces replication errors around a thousand-fold, serving as one of our body’s best defenses against genetic mutations that can lead to cancer.North Carolina State University, “Genome guardians stop and reel in DNA to correct replication errors” at ScienceDaily
Keep moving along, folks, no design to see here…