n cancer cells one allele of the tumor suppressor gene p53 is frequently mutated so that the protein is inactive, not produced,
or deleted. The other allele will usually have a normal sequence and the promoter remains intact but the gene is not expressed. Sequencing with sodium bisulfite modification of DNA can be used to detect which cytosines are methylated. If the cancer cell DNA is sequenced what would be the anticipated results?
If the cancer cell's DNA is sequenced than the anticipated results will be that the cytosines in or close to the promoter region will get methylated. It has been stated that in the cancer cells one allele of p53 is mutated and the other allele, however, of exhibiting an intact promoter, does not express the protein.
Thus, it shows that the expression in the other allele gets suppressed by methylation rather than by mutation. Methylation generally takes place in CpG islands in or close to the promoter region and therefore inhibits transcription.
