Variation may also occur as a result of the selection pressures which different populations are subjected to, for example, in humans, the heritable trait glucose-6-phosphate dehydrogenase (G6PD) deficiency confers a relative degree of protection against the malaria parasite and therefore variations in G6PD are found to a greater extent in populations whose ancestry derives from tropical regions such as Sub-Saharan Africa and Southern Asia (7). The gene discussed is G6PD; the disease is malaria.