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).
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.