Name: _______________
Lac Operon AP Biology PhET Simulation
The goal of this simulation is to help you understand how prokaryotes (note that this is for prokaryotes and NOT
eukaryotes) control gene expression. Specifically, this activity will simulate an inducible operon called the lac operon
used to control the expression of genes that control lactose levels in bacteria. Again, this is for bacteria only and has
nothing to do with lactose catabolism or lactose intolerance in humans.
Step 1: Drag the lac promoter to the stretch of DNA. Do NOT drag the lacZ gene to the DNA. What happens? Why is
this?
RNA polymerase will attach to the lac promoter and go down the DNA to eventually detach.
Step 2: Now try dragging the lacZ gene to the DNA and note what happens.
The RNA polymerase will attach to promoter and go down the DNA, once it gets to lacZ gene, it creates messenger RNA
Step 3: Inject some lactose (about 25 molecules should do it) into the simulation. Note what happens. Specifically, what
is lactose being converted into?
Messenger RNA turns into LacZ, which will then have the lactose bind to it breaking the molecule apart and having it
dissolve.
Step 4: Note that the lac enzyme continues to be produced even in the absence of lactose. Why is this a problem? Try
dragging the lac operator gene onto the stretch of DNA. What is the result?
It is a problem because it could potentially be a problem with how everything functions.
Step 5: Now try adding the lacI promoter and gene to the stretch of DNA. What happens?
RNA polymerase will create LacI
Step 6: Again, add some lactose (and again, 25 molecules should work well) into the simulation. What is the INITIAL
result of adding lactose when both genes are activated?
The lactose will bind to the LacI and stay bonded for a while until it releases it still attached. It will then dissolve
This study source was downloaded by 100000836551366 from CourseHero.com on 02-21-2022 04:29:59 GMT -06:00
https://www.coursehero.com/file/20525869/Lac-Operon-AP-Biology-PhET-Simulation-2/
Lac Operon AP Biology PhET Simulation
The goal of this simulation is to help you understand how prokaryotes (note that this is for prokaryotes and NOT
eukaryotes) control gene expression. Specifically, this activity will simulate an inducible operon called the lac operon
used to control the expression of genes that control lactose levels in bacteria. Again, this is for bacteria only and has
nothing to do with lactose catabolism or lactose intolerance in humans.
Step 1: Drag the lac promoter to the stretch of DNA. Do NOT drag the lacZ gene to the DNA. What happens? Why is
this?
RNA polymerase will attach to the lac promoter and go down the DNA to eventually detach.
Step 2: Now try dragging the lacZ gene to the DNA and note what happens.
The RNA polymerase will attach to promoter and go down the DNA, once it gets to lacZ gene, it creates messenger RNA
Step 3: Inject some lactose (about 25 molecules should do it) into the simulation. Note what happens. Specifically, what
is lactose being converted into?
Messenger RNA turns into LacZ, which will then have the lactose bind to it breaking the molecule apart and having it
dissolve.
Step 4: Note that the lac enzyme continues to be produced even in the absence of lactose. Why is this a problem? Try
dragging the lac operator gene onto the stretch of DNA. What is the result?
It is a problem because it could potentially be a problem with how everything functions.
Step 5: Now try adding the lacI promoter and gene to the stretch of DNA. What happens?
RNA polymerase will create LacI
Step 6: Again, add some lactose (and again, 25 molecules should work well) into the simulation. What is the INITIAL
result of adding lactose when both genes are activated?
The lactose will bind to the LacI and stay bonded for a while until it releases it still attached. It will then dissolve
This study source was downloaded by 100000836551366 from CourseHero.com on 02-21-2022 04:29:59 GMT -06:00
https://www.coursehero.com/file/20525869/Lac-Operon-AP-Biology-PhET-Simulation-2/
