Most of a person’s
inherited characteristics are due to the sequences of units within the genes
making up their DNA, these changing from one generation to the next. Epigenetic
influences refer to additional changes in genes which are not due to changes in
the DNA sequence, but involve the addition or removal of small molecules to the
outside of the gene. These may determine whether the gene is ‘switched on’ or
‘switched off’, thus affecting whether a characteristic coded by the gene is
expressed or not.