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    • #6896
      MrMistery
      Participant

      Ok, so i am doing some reading on DNA replication these days. The book i am reading right now is "Life: the Science of Biology 7th edition". here is a question i have regarding to something i have found.

      It says that if there is an AC pairing during replication, some proteins detect it, but in order to tell if it needs to be GC or AT they must know which is the old strand and which is the new one. And it says: "The repair mechanisms can detect the "wrong" base because a DNA strand is chemically modified some time after replication. In prokaryotes, methyl groups are added to some guanines. Immediately after replication, methylation has not yet occured, so the newly replicated strand is "marked", by being unmethylated, as the one in which errors should be corrected"

      Methylation of guanines? I have only heard of cytosine methylation in DNA. Has anyone ever heard of methylation of guanines?
      And if someone has the 8th edition, can you please look and see if it says guanine methylation there too?(look at chapter 11, at DNA mismatch repair, after DNA methylation).
      Thanks…

    • #68561
      sdekivit
      Participant

      according to ‘Biochemistry’ 5th edition by Berg et al it is the cytosine that is methylated on the C-5 by methyl transferases. I am also familiar with methylated adenine to avoid cleavage by restriction endonucleases.

    • #68562
      MrMistery
      Participant

      ok thanks for the answer. Methylation of adenine to avoid cleavage? good to know. Cause i just read that "the DNA is methylated" in that situation…

    • #68575
      sdekivit
      Participant
      quote MrMistery:

      ok thanks for the answer. Methylation of adenine to avoid cleavage? good to know. Cause i just read that “the DNA is methylated” in that situation…

      for the mismatch reapir system you need to remember the CpG-islands that can be methylated 🙂

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