Question

Which of the following are phenotypes that would result from Tn5 transposition into lacY on the E. coli chromosome (the operon is constructed exactly like was shown in class)

	Survival of a galE deletion mutant on M9 minimal media plates supplemented with lactose and glucose
	Lac-
	White colonies when grown on LB+Xgal (Xgal is not transported by LacY, LacZ diffuses out of the cell)
	No measureable color change of media when cells are grown in media containing ONPG (ONPG is not transported by LacY, LacZ diffuses out of the cell)

Answer 1

Phenotypes that would result from Tn5 transposition into lacY on the E. coli chromosome is

No measureable color change of media when cells are grown in media containing ONPG

(ONPG is not transported by LacY, LacZ diffuses out of the cell).

lacY gene codes for permease which is required for the lactose molecule to cross through bacterial cell.

O-Nitrophenyl-β-D-galactopyranoside (ONPG) is an analog of lactose i,e it is structurally similar to lactose except in ONPG orthonitrophenyl has been substituted for glucose .

Enzyme β-galactosidase cleaves ONPG into two residues, galactose and o-nitrophenol after diffusing out of the cell. like it cleaves lactose into galactose and glucose.