AP Bio Chapter 18 Part 1 Flashcards
What attaches to the operon, or operator site
The repressor
Prokaryotes can have ___________ proteins on the ________ mRNA molecule
Different
Same
What do you “want” concerning gene expression
On at different times, only when you need it to conserve resources
If you want the gene off
Don’t make RNA
In prokaryotes transcription and translation
Happens simultaneously
Coupled
What do prokaryotes regulate and how
Gene expression
Therefore their metabolism
By regulation transcription almost entirely
What makes prokaryotic gene expression efficient
The lack of a nucleus
What are operons
Refer to clusters of genes that all contribute to a particular metabolic task
What uses operons for gene regulation
Prokaryotes
What is basically operon regulation
On switch/off switch a bunch of genes do the same thing
What are the two types of operons
Inducible and repressible
What are some characteristics of the lac operon
Digest lactose, inducible, positive feedback
What are some characteristics of trp operon
Synthesize tryptophan, repressible, negative feedback
Inducible
For metabolic pathways that are usually “off”
Promoter transcription factor and RNA polymerase bind where
Upstream of the gene they’re activating
When lactose is absent,
The repress of protein (made by Lacl gene) is able to attach to the operator
RNA polymerase cannot transcribe the structural genes (La Z, Y, A) that the cell needs to be able to digest lactose, since it can not attach to the promoter
This is how things remain in the cell as long as there is no lactose present
What is the operator
A region of the promoter where the recession protein binds
When lactose is present,
The inducer molecule (allolactose, a form of lactose) binds to the repressor protein
This changes the shape of the repressor protein so that it can not attach to the promoter
RNA polymerase is then able to transcribe the structural genes that the cell needs to digest lactose
This is how things remain in the cell until lactose is digested
Repressible
For metabolic pathways that are usually on
Ex. Trp (synthesizes tryptophan)
When tryptophan is absent
- the repressor protein (made by the TrpR gene) is unable to attach to the operator
- RNA polymerase can transcribe the structural genes that the cell needs to be able to synthesize tryptophan
- this is how things remain in the cell as long as there is no tryptophan present
When tryptophan is present
The corepressor molecule (tryptophan) binds to the repressor protein
This changes the shape of the repressor protein so that it can attach to the promoter
RNA polymerase can not transcribe the structural genes that the cell uses to synthesize tryptophan
This is how things remain in the cell until tryptophan is no longer present
Up regulation
Ways to increase the rate of transcription of an operon
Down regulation
Ways to decrease the rate of transcription of an operon
