General Notes
This modification alters the structure of cytosine but not its base-pairing properties. The timing and function of cytosine methylation varies amongst species with roles in such processing events as transcription and recombination. For example, in mammals, methylation occuring during early development and emrbyogensis functions in X chromosome inactivation and gene imprinting, wherease in plants, DNA methylation occurs later and affects genomic stability through silencing of transposable elements .The deamination of 5-MeC results in the formation of thymine (T) instead of uracil. Since thymine is not recognized by DNA repair enzymes, cytosine to thymine conversions can cause transition mutations. The most frequent mutations in human genetic diseases are those involving C to T transitions occurring at CG sites . Another type of mutation involving 5-MeC involves the formation of pyrimidine dimers. Upon exposure to sunlight, pyrimidine dimers form preferentially at dipyrimidine sequences containing 5-MeC, a mutation frequently seen in human skin cancers . Sheep Anti-5-MeC is reported as suitable for use in immunocytochemistry.