Genome complexity: DNA repair molecule (Introduction)

by David Turell , Tuesday, November 10, 2015, 01:10 (3090 days ago) @ David Turell

Here is another repair mechanism using a specific molecule:-http://phys.org/news/2015-11-search-and-rescue-proteins-dna-mutations-linked.html-"MutS is the first protein involved in DNA mismatch repair and is responsible for detecting rare errors that can predispose people to certain types of cancer, a hereditary condition called Lynch syndrome or cancer family syndrome. If a person's mismatch repair system is hindered, the mutation rate increases 100-to-1,000 fold, Simmons said.-***-"To see the protein, the researchers fused MutS to a fluorescent tag and activated fluorescence with a laser. They then could track individual molecules moving through the living cell, similar to a spotlight following a person around a crowded room, Simmons said.-"They found that MutS moved fast to canvas the entire nucleoid, and then slowed significantly when it reached the spot where DNA is replicated. MutS identified and fixed mismatches at this replication site.-"Our work indicates that the population that is moving rapidly isn't searching for mismatches but rather searching for the site of replication," Simmons said. "Once there, it slows down and searches for errors as the DNA is being synthesized."-"There are four DNA bases that are arranged in pairs, and each has only one specific pairing partner. The base pairs hold together the two helix strands of DNA, and a mismatch occurs when the wrong partner is paired with the original DNA base. Hereditary information is passed on when these strands of DNA replicate, and mistakes in replication can lead to cancers.-"The mismatched pair kinks the DNA at the replication fork where DNA is made, Biteen said. MutS positions itself at that fork so it's ready to catch any mistakes. As an added bonus, this positioning likely tells MutS which side is correct and which side is the new, altered DNA."-Comment: Since this protein is so specific, how was it found after DNA developed and suffered copy errors. Could it be that DNA and its repair mechanism were designed together?