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Alleles and populations

Some alleles spread through a population because the people that have them are more likely to survive, and to pass those alleles on to future generations. For example, peoples living in hot countries have alleles that give them darker skin. Their skin contains more of the pigment melanin, which absorbs the sun's harmful rays and prevents damage to the surrounding cells.

Several genes influence skin colour.
Several genes influence skin colour.
Corbis

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