Question

1. Describe the lac operon and its regulation. Figures can be helpful for darity, but are not required. 2. Describe the wild-type E. coli phenotype for beta-galactosidase expression in glucose-rich, lactose-rich, and glucose/lactose-rich environments. 3. What is ONPG, and why is it used to determine the levels of beta-galactosidase activity? 4. Explain the control(s) used in the experiment. 5. Explain any sources of error in this experiment: if the experiment didn't go as planned, give at least one reason why that might have happened. If it did go as planned, still give an example of something that might have caused an error.

Answer 1

Answer-

According to the given question-

Lac operon-

Expression of genes can be transcriptionally regulated which are occur in both eukaryotic as well as prokaryotic cells. organisms.

one such was using the gene that are used to ferment lactose in E. coli. Three genes which are clustered together are required by E. coli to utilize lactose. lac Z gene code for Beta galactosidase, lac Y gene code for lactose permease and lac A gene code for galactoside transacetylase. There is lac P which is promoter region needed for transcription of lacZ, lacY and lac A gene as a polycistronic mRNA. lac O is operator site involved in transcriptional regulation of lac operon. these are collectively called lac operon. there is lac I regulatory gene that code for a mRNA that translated to produce a protein called lac repressor protein.

Regulator here Operator I CARR K structurals DNA UZHA Lac 2 lac Y llac A LOCT 1 | 1 DR -Qalaetosidase Transactylase - 1 promatera B-galactosidase a Repressor B-galactosidase bermeape gene Repressor protein

Condition 1- High glucose , No lactose-

High glucose, no lactose Scenario-1 - (CAP) RNA palymerase) when glucose es high then no cAMP es. produced due to which CAP alone cannot bind with DNA that leads to very lact low level of Transcription Regulator promater operator lacz lacy Repressor gene x ho transcription af lactose metabolism righ glucose Repressor proten enzymes → care with Rebressor byetem binds with operator and RNA polymerase binds with the premotor but unable to move part operator because the operator was blocked by the Repressor due to which Genes that code for Lactose hectabalym not transcribed.

Condition 2- No glucose , High lactose-

Scenario 2- No glucose High Lactose I RNA CAMP es produced because of low level of glucose now the CAMP binds the CAP and bath bind with DNA which help RNA baly - merase to bind with bromatar and trans- -cription occur. CAMP pal operator CAP promater I Iloer VITA lae 2 | lacy llach Repressorgene er geny are transcribed Ripressor Z righ lactose. lactose binds with Repressor changing its stape due to drech Repressor Cannat bind to operator and RNA polymerase can move post operator and Transcribed the gene for lactose metabolum. This leads to breakdown of lactose and galactose. auto glucose

Condition 3- High glucose , High lactose-

mono-3 - High glucose, High lactose due to high glucose the CAP as Tow due to check the CAP alone. cannot bind with pred same Time the lactose binds with repressor and prevent the binding of Repressor weith operator. lae A RNA bol Operator Lae z locy low Transcription level of occur Repressor binds lactose Repressor and prevent its binding efter promotor.

ONPG - is also called O-nitrophenyl ß-galactoside which is used as analogue of lactose and by using it we can measure the activity of ß-galactosidase which convert the medium from colourless to yellow due to fromation of o-nitrophenol and also galactose which is coloueless. here the Galactose work as a competitive inhibitor with ONPG for binding with the ß-galactosidase. while iodine solution is used as non-competitive inhibitor.

Scenario - 4 - No glucose no-lactose - CAMP levels is high and which bruds with CAP and boyu birds with Dren. PNER pol CAMP (CAP) promoter operator laez laey lach Depressor Arine neo Transcription occur. Repressor 2 Binds with operator and block the movement of RNA polymerase due to which Transcription does not occur.