Could someone explain why it is B and not C B11) (4 points) You mate an Hfr stra
ID: 265973 • Letter: C
Question
Could someone explain why it is B and not C
B11) (4 points) You mate an Hfr strain that is Amp (sensitive to the antibiotic ampicillin), Lact, Asp, Leu' to a F strain that is Amp Lac Asp Leu. You know that Lac is the last gene to be transferred by this Hfr strain and that Amps is not transferred at all You select 1000 Lac Amp progeny and screen for the Asp & Leu markers. The following numbers of each phenotype are obtained (all are Lac Amp) Asp Leu 475 Asp* Leu1 Asp Leu 30 Asp Leu 70 What is the order of the genes? A) ORT-Lac-Asp-Leu.;B) ORT-Asp-Leu-Lac; C) ORT-Leu-Asp-Lac.Explanation / Answer
Hfr is the high frequency recominant formed when the plasmid integrates with the bacterial chromosome. It has more potency to conjugate with the F-. But during conjugation, the bacterial cells do not conjugate for longer time and all the genes cannot be transfered to the F-.
The order of genes is ORT-Asp-Leu-Lac because the number of bacterial cells found with both the genes Asp+-Leu+ are more than the other combinations.