Epigenetics is a relatively new field in
molecular biology, the study of heritable traits that don't involve a change in
gene sequence. The expression of genes can be affected in a heritable fashion, even if the
DNA sequence in the
nucleus remains the same. This could be a consequence of a difference in DNA
methylation or in
chromatin structure. Another option could involve the genomes of cytoplasmic elements (
chloroplasts and
mitochondria). Other mechanisms have also been proposed. The phenomenon was first observed in plants. See
epigenetic inheritance for a more detailed discussion.
The epigenome is the overal epigenetic state of an organism.