Question

What role does DNA methylation play in evolution? Use a specific example to support your prediction.

Answer 1

DNA methylation plays an important role in evolution-
1 it is associated with important epigenetic processes such as genomic imprinting, histone modification and X chromosome inactivation.
2 Methylation occurs maily at 5 - Cytosine region,when it occurs in CpG islands found in the 5′ regulatory regions including the promoter regions in mammals, promotes gene silencing. Mainly the viral DNA or transposable element are often repressed by DNA methylation. Thus silencing mutations in constitutive genes.
3 DNA methylation in Non-CpG has been observed in mammals, with high percentages in embryonic stem cells. These cells are highly conserved during evolution and methylation helps to maintain this.  

The best example are the human.

In human and other mammals during the first few embryonic replication cycles of morula and blastula,the rate of DNA methylation increases,with CpG islands protected from methylation. This results in repression of other genes and allows housekeeping genes to be expressed in all cells.
Methylation pattern are stage and tissue specific with changes that would define each individual cell type lasting stably over a long period,during post implantation.