WAEC - Biology (2009 - No. 51)
The allele responsible for sickle-cell anaemia first appeared in the tropical and subtropical regions of Asia, the Middle
East and Africa. It entered the United States of America when individuals were forcibly brought over from Africa. In micro-
evolutionary terms this is an example of
East and Africa. It entered the United States of America when individuals were forcibly brought over from Africa. In micro-
evolutionary terms this is an example of
mutation
gene flow
genetic drift
natural selection