Question

The following activity will give you practice with the two operons we discussed - the lac operon and the trp operon. Below are two scenarios to consider. You will need to determine whether or not transcription is occurring and describe what is happening in the cell using our operon vocabulary words - regulatory gene, RNA polymerase, operator, promoter, repressor, and genes. 1. Bobby Joe just enjoyed an In and Out milkshake, how will the E. coli in her stomach respond? a) For the lac operon, will the repressor or RNA polymerase be bound to the operon in this situation? Draw what will be happening on the operon below. OPERATOR Lactose Enayme 1 Lactose Enyre à Lactose Enzyme b) Will transcription occur? c) Describe what is happening (with vocabulary words). YES NO 2. in her stomach respond? Bobby Joe just enjoyed a turkey sandwich (turkey is high in tryptophan), how will the E. coli in this situation? Draw what will be happening on the operon below. PROMOTERİ OPERATOR |Tryptophan Enzyme 1|Tryptophan Enzymetryptophan Erame a) For the trp operon, will the repressor or RNA polymerase be bound to the operon b) Will transcription occur? c) Describe what is happening (with vocabulary words) YES NO Practice with Operons The following activity will give you practice with the two operons we discussed - the lac operon and the trp operon. Below are two scenarios to consider. You will need to determine whether or vocabulary words-regulatory gene, RNA polymerase, operator, promoter, repressor, and genes. 1. Bobby Joe just enjoyed a dairy-free Boba drink, how will the E.coli in her stomach respond? in this situation? Draw what will be happening on the operon below not transcription is occurring and describe what is happening in the cell using our operon a) For the lac operon, will the repressor or RNA polymerase be bound to the operon

Answer 1

1, lac operon of E.coli contain genes in lactose metabolism with the respond of on and out to lactose and glucose level: the lac Repressors and catabolite activator protein (CAP)..lac Repressors blocks transcription of the operon,but stops acting as a Repressors when lactose is present..catabolite activator protein (CAP) acts as a glucose sensor..it activates transcription of the operon,when glucose levels are low..

The lac operon with single promoter (mRNA) genes encodes proteins it allow the bacteria to use lactose as energy source..

B, yes transcription occur..

C, The lac operon contain three genes lac Z, lacY,lacA ..these are transcribed as a single mRNA,under control of one promoter and it also contains a number of regulator DNAwhich regulates proteins it can bind, control transcription of the operon..The promoter is the binding site for RNA polymerase,the enzyme that performs transcription..CAP is binding site promotes transcription by helping RNA polymerase bind to the promoter..

- when glucose present, lactose absent no transcription of the lac operon occur..cAMP levels will be low due to glucose levels high..so CAP inactive it can not bind DNA..

- when glucose present, lactose absent low transcription of the lac operon occur..CAP inactive and can not bind to DNA..lac Repressors released from operator because allolactose is present..

- when glucose absent,lactose absent no transcription of the lac operon occur..cAMP high due to glucose levels are low..CAP active bound to the DNA.. allolactose absent RNA polymerase present transcription..

- glucose absent, lactose present strong transcription of the lac operon occur..allolactose is present..cAMP levels are high due to glucose is absent..CAP helps RNA polymerase bind to the promoter..high levels of transcription occur..