Assume you are setting up transformations with EColi using s

Assume you are setting up transformations with E.Coli using selective media containing Ampicillin,X-gal, and IPTG.

What would the most likely phenotype of an E.Coli colony containing pUC18 ( without an insert fragment) be if the following mutations occurred early in the growth of a single cell into a colony on your plate?

- A FRAMESHIFT MUTATION IN THE FIFTH CODON LACZ GENE IN pUC18

-A LOSS OF the pUC plasmid

- A deletion of bps at positions 19-25 of the Ampicillin resistence gene open reading frame

Solution

A frameshift mutation in the fifth codon lacZ gene in pUC18 will result in formation of blue colonies in the plate.This is because even if the fifth codon undergoes mutation and there occurs shift in reading frame, the mutant E.coli will undergo alpha complementation to produce beta galactosidase and so blue colonies will be seen Loss of pUC plasmid will not infer antibiotic resistance and formation of beta galacosidase will not take place..So,colonies will be white in color but since they will not be antibiotic resistant,no colonies will be seen. A deletion of bps at positions 19-25 of the Ampicillin resistence gene open reading frame will result in translation of a mutated beta lactamase that will not be able to confer antibiotic resistance any more.So, no colonies will be seen in the plate.