Deletion due to unequal crossing-over within a gene

Marked sequence homology of certain regions
of the globin genes may lead to nonhomologous
pairing and unequal crossing-over during
meiosis, e.g., in the regions of codons 90–94 of
one DNA strand and codons 95–98 of the other.
This explains the deletion of codons 91–95 in
hemoglobin Gun Hill.