Point  mutation in hemoglobin
   gene.
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   In  this  point  mutation,  the DNA template strand has an A where the
   wild-type template has a T (base-pair substitution).
   The mutant mRNA has a U instead of an A in one codon.
   The  mutant  (sickle-cell)  hemoglobin has a valine (Val) instead of a
   glutamic acid (Glu).