Revertants of a number of spontaneousmutants | Homework Helpers

Proflavin-induced wild-type revertants of a number of spontaneousmutants in ac+ gene of phage T4 were isolated. Proflavin induces frameshift mutations. The aminoacid sequence of the affected protein was analyzed in several of these revertants. The affectedstretch of amino acids is shown for one such pseudo-wild type revertant (also shown are the amino acidsin the true wild type protein).

Using the genetic code table in you book, reconstruct the twomutational events [the original ac+ —

> ac- spontaneous mutation (the amino acid sequence of themutant intermediate is unknown) and the proflavin-induced ac- -> ac+ reversion mutation creating apseudo-wild type revertant with the amino acid sequence given in the bottom line.

True wild type (ac+) …ILE PHE LEU ALA SER ASP CYS

Spontaneous mutant (ac-) … ? ? ? ? ? ? ?

Revertant strain (ac+) …ILE SER TRP LEU VAL ASP CYS

* The revertant strain has a wild type phenotype but is not a truewild type revertant

(as the amino acid sequence indicates)