Even though disease-associated alleles are probably not neutral, even slightly deleterious alleles may increase in frequency because of founder effects.
For most of humanity’s existence, sickle cell disease usually meant an early death, most likely... 8 Meleda Disease. Founder effects have been used to explain the presence of high-frequency Mendelian diseases in many isolated populations (Thompson and Neel 1996; Vogel and Motulsky 1996).
Photo credit: Baujat G, Le Merrer M. Though this particular syndrome isn’t exclusive to... 9 Sickle Cell Disease.
The effect on the genetic makeup of a population can be quite profound, as the prevalence of disease can increase.
The syndrome is commonly found among the Old Order Amish of Pennsylvania, a population that experiences the " founder effect."
The founder effect is a case of genetic driftin which a small population of a limited number of individuals breaks off from a larger population. Top 10 Examples Of Founder Effects 10 Ellis-van Creveld Syndrome.