DNA Mismatch Repair: Distinguishing Faulty Daughter Strands

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In summary, methylation plays a crucial role in differentiating between parental and daughter strands with mismatch nucleotides. This is because newly synthesized DNA is hemimethylated, allowing GATC endonuclease and GATC exonuclease to identify and nick the mismatch nucleotide sequences. However, it is unclear how the faulty daughter strands are distinguished from normal daughter strands without methylation. This distinction is recognized through a distortion of the normal DNA double helix. It is important to note that the discussion of methylation is specific to either a bacterial system (6-adenine) or mammalian (5-cytosine) methylation system. Without methylation, the enzymes would not be able to determine which strand is the
  • #1
weng cheong
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i understand that methylation helps to differentiate between parental strand and daughter strand with mismatch nucleotides. (newly synthesised DNA is hemimethylated)
then GATC endonuclease and GATC exonuclease will nick the mismatch nucleotide sequences.

however, i don't understand how the faulty daughter strand are distinguished from normal daughter strand?
 
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  • #2
What is recognised is the mismatch surely? A distortion of the normal DNA double helix.

What text are you working from and does it not say that somewhere?

And is it talking about a bacterial system (6-adenine) or mammalian (5-cytosine) methylation system?

If there is a mismatch the enzymes could not distinguish which strand was 'right' i,e, parental and which 'wrong' i.e. daughter without the methylation.
 
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  • #3
In DNA replication you start out with one double stranded DNA consisting of two parental strands. After replication, you have two double stranded DNA and each of these DNA molecules contains one parental strand connected to one daughter strand. Therefore, you don't need to distinguish between daughter strands as they are on different molecules of DNA.
 

1. What is DNA mismatch repair?

DNA mismatch repair is a cellular process that corrects errors that occur during DNA replication. It involves the detection and removal of incorrect base pairs (mismatches) that may have been incorporated into the newly synthesized DNA strand.

2. How does DNA mismatch repair work?

DNA mismatch repair is carried out by a group of enzymes that recognize the mismatched base pairs and remove the incorrect nucleotide from the daughter strand. The missing nucleotide is then replaced with the correct one, ensuring that the DNA sequence is accurate.

3. What happens if DNA mismatch repair fails?

If DNA mismatch repair fails, the daughter strand will contain errors (mutations) that can lead to various genetic disorders and diseases. These mutations can also accumulate over time, increasing the risk of developing certain types of cancer.

4. What causes DNA mismatches to occur?

DNA mismatches can occur due to errors during DNA replication, exposure to mutagens (agents that cause mutations), or natural changes in the DNA sequence. They can also be caused by inherited genetic mutations that affect the DNA repair enzymes.

5. How is DNA mismatch repair related to genetic diversity?

DNA mismatch repair plays a crucial role in maintaining the accuracy of the genetic code. However, it also contributes to genetic diversity by introducing small variations in the DNA sequence through the occasional incorporation of incorrect base pairs. This diversity is essential for evolution and the adaptation of species to changing environments.

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