ENVIRONMENTAL INFLUENCES (EPIGENETICS)

=Environmental Influences= ''' GENOTYPE + ENVIRONMENT → PHENOTYPE''' Clearly the environment is also responsible for some of the variation seen between individuals. The environment will influence an individual from the moment of conception (or even before!); various factors in the womb can affect gene expression and thus a child’s development. Such external factors that influence gene expression are known as epigenetic factors. There is also great debate about how much influence a person’s genetic make-up vs. their upbringing has on characteristics such as aggression. This is often referred to as the ‘nature vs. nurture’ debate Many environmental factors will affect gene expression, for instance the two highlighted butterflies below were originally thought to be different species. However, this is actually the result of a change in gene expression to temperature; the top left form is the summer form while the bottom right is the spring form. [image:http://i.imgur.com/FzSDhuy.png] A slightly more bizarre response to environmental conditions is exhibited in the Himalayan rabbit, which will grow white or black fur depending on the temperature (this is why its extremities are usually black –they are colder). Placing an ice pack on a shaved patch will result in a black patch. [image:http://i.imgur.com/DFkuHWe.png] Another interesting response to temperature can be noted in the Nile crocodile. Here, the sex of a baby crocodile is determined by the temperature at which the eggs are kept! However, the environmental influence on gene expression can be as simple as the fact that when we eat food, the expression of digestive enzymes is increased.