Twins: Identical twins are rarely exactly the same, despite sharing the same DNA code. In extreme cases, one twin may have a devastating disease such as schizophrenia while the other is healthy. This disparity reflects growing epigenetic differences between the twins, usually as a combination of responses to the environment and also random variability in the epigenetic modifications in their cells.
Seabass: Mammal gender is genetically determined, based on the presence or absence of a Y chromosome. However, in young European sea bass, water temperature causes epigenetic changes, and this determines their gender. There’s a similar mechanism in crocodiles. It’s possible, therefore, that climate change may disrupt sex distribution in
Bees: Queen bees are physically very different from workers, and can live 20 times longer. But there’s nothing genetically special about queen bees: they are just the product of a different feeding regime in early life. This leads to epigenetic modifications that maintain queenly gene expression patterns.
Cats: Almost all tortoiseshell cats are female. The orange and black coat colour genes are carried on the female sex chromosomes, known as X chromosomes. One of each pair of X chromosomes is randomly silenced by epigenetics early in development, and this creates the beautiful patchwork patterns in the feline fur.