Question

Q1. PLEASE EXPLAIN THE ANSWER Near to lacO are other DNA sequences similar to lacO.

A. What prevents LacI from occupying these instead of the lacO in the promoter region?

B. What role is proposed for those other lacO-like elements?

Q2. PLEASE EXPLAIN THE ANSWER

You are given an E. coli merodiploid with an F plasmid with this genotype: lacP- lacO+ lacZ+ lacY+ and a chromosome with a second copy of the lac operon with this genotype: lacP+ lacO+ lacZ- lacY-. Depending on the whether lacP- is replaced with lacP+ on the F plasmid by the Holliday or DSBR model, what happens to the copy of lacP on the chromosome? Explain why.

Answer 1

A. Ans- The gene that encodes the lac repressor is named lacI and it's under control of its own promoter. The lacI gene happens to be found near the lac operon, but it's not a part of the operon and it's expressed separately. LacI binding in living yeast cells using a fluorescent repressor operator system that found prevention by genetically altering that includes GFP lacI structure, GFP lacI stability, chromosome accessibility, lacO sequence that reduced the GFP tagging location and fusion protein stability have a large effects on lacI binding.

B. Ans- On the addition of lactose, which changes its binding affinity for the lacO sequences and transcription occurs. E.coli uses this system to tightly control the genes required for the use of lactose. For those other lacO like elements are responsible for producing a repressor protein. In the presence of allolactose, a binary complex is formed between allolactose and the repressor that makes binding of the repressor of the operator region impossible.

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