A strain of E. coli carries a mutation that
completely inactivates the enzyme encoded in the gene. Several
revertants, mutants of the mutant with partly or fully restored
activity, were selected, and the amino acid sequence of the enzyme
was determined. The only differences found were at position 10 in
the polypeptide chain.
Revertant 1 had Thr.
Revertant 2 had Glu.
Revertant 3 had Met.
Revertant 4 had Arg.
Assume that the initial mutation itself, as well as each
revertant,...