iGenetics 3rd Edition by Peter Russell

Exercise 6

Some complete loss-of-function mutations result from a deletion of just one gene or a missense mutation that results in a completely nonfunctional protein
a. If such mutations were obtained in each of the lacA , lacI , lacY , and lacZ genes, which would show a lac phenotype (be unable to grow using lactose as a sole carbon source)? What properties would the other(s) show?
b. If such mutations were obtained in each of the trpA , trpB , trpC , trpD , and trpR genes, which would show a trp phenotype (require supplemental tryptophan for growth)? What properties would the other(s) show?
c. If such mutations were obtained in each of the araA , araB , araC , and araD genes, which would show an ara phenotype (be unable to grow using arabinose as the sole carbon source)? What properties would the other(s) show?