Evaluating genetic and environmental effects
a) In plants;
- Plants of a known genotype can be cloned to produce genetically identical plants. These plants
- can then be grown in different environments. If the appropriate controls are in place, the
- variations that occur in the plants can be thought to be caused by the environment that they are
b) In Animals:
- This method can include studying two identical twins who have been brought up in distinctly
- different environments. This will show how environmental factors contribute to variation.
- Variations in genetic factors can also be studied using this method. A large sample of identical
- and non-identical twins in similar environments are studied. If there is more variation between
- the non-identical twins than the identical twins, the variations are assumed to be mainly due to
- genetic factors.
Example;
> Overeating was thought to be caused by only the environment, such as factors like increased availability of food in developed countries.
> It was later discovered that food consumption increases brain Dopamine levels.
> Once enough Dopamine was released, people would stop eating.
> Researchers found that people with one particular allele had 30% fewer Dopamine receptors.
> This meant that these people wouldn’t stop eating as their Dopamine levels increased.
> This meant these people were more likely to overeat.
> Based on this evidence, scientists now think that overeating has both genetic and environmental causes.
Example;
> Many foods in our diet contain antioxidants, which are thought to play a key role in preventing chronic diseases.
> Foods such as berries contain high levels of antioxidants.
> Scientists thought that the number of antioxidants that different berries contained was due to genetic factors.
> But experiments that were carried out to investigate the effects of the environment on antioxidant levels showed a great deal of variation.
> Scientists now believe that antioxidant levels are due to both genetic and environmental factors.
