Inbreeding among relatives reduces
   genetic variation by decreasing heterozygote frequency.

   In   the  extreme  form  of  inbreeding,  self-fertilization,  for  an
   individual  heterozygous  at  one  locus,  94%  of its descendants are
   homozygous in 4 generations.

   Note, however, that the allele frequencies of A and a remain unchanged
   at 50%.