Epigenetic control of gene expression

Ever since James Watson and Francis Crick proposed the double-helix model in 1953, it has been taken as fact that DNA possesses the instructions for making all parts of an organism. In recent years, however, we have come to realise that DNA is only part of the story of heredity. It is accepted that while genes determine the features of an organism, the environment can influence the expression of these genes (Topic 18.2). However, the changes they cause to the phencrype were thought not to be inherited by the offspring. We now believe that environmental factors can cause heritable changes in gene function without changing the base sequence of DNA. This process is known as epigenetics.