Variation
If people who have the sickle-cell gene (S)
have a greater tendency to die before they reproduce, then we would expect to
see only a small amount of the sickle-cell gene in the general population.
However, even though many SS babies
die of sickle-cell, we still find that about 1 out of every 4 people have the
S gene and are AS.
How can this fact be explained?
Long & Slichter