Genetics Intelligent Design

Researchers: Proofreading proteins prevent DNA errors

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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

Paper 1 (paywall) and Paper 2 (paywall).

Keep moving along, folks, no design to see here…

7 Replies to “Researchers: Proofreading proteins prevent DNA errors

  1. 1
    polistra says:

    Those numbers are impressive! Average 600 errors per division, and the proofreaders reduce the error by 1000. In other words, they reduce the average errors per division to 0.6, less than one.

    It’s instructive that human quality control procedures, when they’re meant to work at all, use the same procedure. Real QC demands shutting down the assembly line as soon as a significant error is spotted. All items produced in the same batch are then either discarded or rebuilt.

  2. 2
    martin_r says:

    so how absurd absurd absurd is Darwinian theory of random mutations ?

    After discovering all these proofreading/repair systems (there are many), how can a reasonable highly educated person (e.g. a Darwinian scientist) still believe in such a materialistic (no foresight) theory ?

    What is wrong with all these Darwinian scientists around the world ?

    It is look like there is some global outbreak of some yet unknown virus causing serious mental-illness …

    or is it really all about grants’ money ?

  3. 3
    kairosfocus says:

    Folks, proof-reading is a code oriented linguistic function. Here, in an algorithmic, goal-directed context. Language and goal-direction are both exceedingly strong signs of rational intelligence and design. KF

  4. 4
    kairosfocus says:

    MR, money can become a demonic gateway and power. KF

  5. 5
    ET says:

    As if blind and mindless processes can account for proof-reading. It is so shameful that evolutionary biology is caught in the grips of materialistic dogma.

  6. 6
    es58 says:

    Technically the use of the word “error” is illogical because blind processes can’t have a right and wrong. We just happen to call it a réplication function (because that’s what it looks like ) . Don’t they ever get tired of this insanity?

  7. 7
    Querius says:

    Good point, Es58.

    But the key is having a name for something. Naming a process is apparently identical with understanding it. So, one can reply to a challenge simply by saying, “Oh, that’s just an ordinary replication function. It’s well understood.” See? 😉

    The video nicely illustrates an absolutely stunning multi-step repair process! And just to think that all these repair processes involving molecular machines supposedly evolved simply by trial and error.


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