What is epigenetics?
Is the study of heritable and potentially reversible gene-expression changes that do not involve structural alterations in the DNA sequence, such as mutations. Is emerging as one of the most dynamic and vibrant biomedical areas . EPIGENETICS MECHANISMS
Epigenetics is the study of heritable and potentially reversible gene expression changes that do not involve structural alterations. DNA sequence,such as mutations.This term was coined to describe changes that could not be explained by genetic mechanisms .These major types of epigenetic changes have been describe:DNA methylation, covalent post translational histone modification and small inhibitory RNA-mediated signaling pathways. DNA methylation is the most extensively studied epigenetic modification in humans. Epigenetic reprogramming during mammalian development
In at least two developmental stags in mammals ,gametogenesis and pre-implantation development ,the DNA methylation pattern is reprogrammed genome-wide. This epigenetic reprogramming is believed to be necessary for return to pluripotency and for lineage commitment. In mammals, the genomes of mature sperm cells and egg remain highly methylated until fertilization. During pre-implantation development, a second round of demethylation takes place in the zygote, occuring at different rates in the two parental genomes. Demethylation of the paternal genome- occurs after fertilization but before cell division, it is more rapid than in the maternal genome, and involves an active mechanism. Demethylation of the maternal genome- occurs gradually over the first few cleavage divisions of the embryo, involves a passive mechanism, and is dependent on DNA replication Both the paternal and the maternal genomes are remethylated around the time of implantation.
Epigenetics and cancer