Question and Answer: Methylation Information

It is interesting in reading some of the discussions in the world of highly advanced DNA. Yet, we still don’t know a lot of this particular area. From a Christian standpoint, it gives God the glory. The remarkable design created by God and it’s various functions from what we know so far, is quite astounding. Here is a brief technical discussion between two people who believe in intelligent design regarding the function of coding and replication of DNA…

Clarifying the question: I am asking if the methylation information (“epigenetic code”) is translated into “genetic code” (nucleotide sequences translating to “insert here” or whatever) or if the protein itself is synthesized as part of the replication process and attached to backbone of the ‘new’ DNA helixes in its original spot.

Answer to the question: Apologies if this spells out things you already know. I wanted to make sure everything is clear. No, the methylation isn’t not translated into “genetic code.” As you say, when DNA is replicated, the old strands are separated and used as template to synthesize a new strand.

The epigenetic information is the methyl groups attached to cytosine residues. Typically, methylation “silences” DNA by preventing transcription, so if you are thinking in terms of information or code, methylation means “don’t express this.” Since different cells express different genes, the pattern of methylation will be different in different cell types and it is important to maintain that pattern when cells replicate.

When the DNA is replicated, the new strand is built using unmethylated cytosines. The DNA is now hemi-methylated — methylated on only one strand. In order for the epigenetic information to be successfully passed on to the daughter cells, the new strand of DNA must be methylated in the same way as the parent strand . Not all CpG dinucleotides are methylated, so a process is needed to selectively methylate the same nucleotides in the daughter strand as are methylated in the template.

At the time of DNA replication, UHRF1 is already floating around in the nucleus. The details of UHRF1 structure are above my pay grade, but from what I can understand, the UHRF1 protein contains a pocket whose size and other biochemical features allow it to bind methylated cystosines in hemi-methylated DNA. UHRF1 does not bind to unmethylated cytosines.

The UHRF1 also binds to a DNA methylase. Since the DNA methylase is now in close proximity to the unmethylated cystosine of the daughter strand, it can now transfer a methyl group to the unmethylated base in the daughter strand. For bases that are unmethylated in the parent strand, UHRF1 will not bind, and the equivalent base will not be methylated in the daughter strand.

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