Question

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see?

1) increased chromatin condensation
2) decreased chromatin condensation
3) activation of histone tails for enzymatic function
4) decreased binding of transcription factors
5) inactivation of the selected genes

Answer 1

Increased cytosine methylation in a mammalian system is likely to lead to the inactivation of selected genes through chromatin condensation and reduced gene expression, as methylated CpG islands within gene promoters signify transcriptional silence.

Step-by-step explanation:

The researcher who manipulated methylation of C nucleotides in embryonic cells in culture would most likely see increased chromatin condensation. Methylation of DNA, specifically methylating cytosine nucleotides, is known to promote chromatin condensation and transcriptional repression. This is because methylation attracts proteins that cause chromatin to pack together tightly, making it difficult for transcription factors to access and bind to DNA, resulting in decreased gene expression.

Upon increased methylation of C nucleotides in a mammalian system, the researcher would most likely see inactivation of the selected genes (option 5). Methylation of cytosine nucleotides is a form of epigenetic regulation that commonly correlates with reduced gene expression. This modification leads to chromatin condensation, rendering the DNA less accessible for transcription and thus silences gene expression. When it comes to the promoters of genes, the presence of methylated CpG islands usually indicates transcriptional inactivity. This tightly coiled chromatin structure does not allow transcription factors to bind effectively, which results in gene inactivation.