Notes 1a Flashcards
Do organisms code make copies of every gene they have?
No, when e. coli uses glucose it only makes about 800 even though it has enough DNA to code for 2000 to 4000
What is a promoter on a gene sequence
sequence of DNA that RNA polymerase binds to “START HERE”
-RNA polymerase’s job is to convert DNA sequence to messenger RNA (mRNA) by Transcription
What is the structural gene on a gene sequence
Directions for making protein or RNA
What is the transcriptional stop on a gene sequence?
- Maybe a loop of DNA
- RNA polymerase falls off = stop here
What are the main components of a gene?
- Promoter
- Structural gene
- Transcriptional stop
What happens after transcription?
The mRNA moves to the ribosome to be translated into a protein.
Why are operons useful
It is more efficient to turn on and off entire pathways at once
What are the parts of a operon
- Promoter
2. Operator
What is the promoter of an operon?
The RNA polymerase binding site.
-When repressor is bound, RNA polymerase is bloked from transcribing the genes in the operon
How does the repressor protein bind to the DNA
by inserting part of itself into the major groove of the DNA
What is the highly conserved method of binding to DNA do repressors use?
Helix-turn-helix motif
-this method of binding to DNA involes inserting one helix into the major groove and the other helix helps maintain the correct geometry for binding
What method do many DNA binding proteins use for binding to specific use sequences of DNA
Helix turn Helix
What is an example of the lac operon
Coliforms are a group of Gram negative rod shaped bacteria used in water quality testing.
- They can use glucose or lactose
- All the genes needed to use lactose are know as the lac operon
What can lactose be broken into?
1 unit of glucose and 1 unit of galactose
What has to happen before a cell can use lactose
Converted into glucose
What does a cell use if glucose and lactose are present
a lac repressor protein binds to the operator sequence and the lac operon shuts off. This stops the production of the mRNA used to made enzymes to break down lactose
Are there any copies of the LacZ protein when glucose is present
Yes, 3 copies LacZ / cell are always present in the uninduced state due to the repressor protein occasionally falling off just when RNA polymerase arrives.
What is the inducer of the lac operon?
allolactase. which binds to the repressor protein. It is a converted version of the low level of lactose (minor product)
How does allolactose work?
Allolactose binds to repressor protein, causing it to change shape and fall off DNA Therefore RNA polymerase can bind
Define catabolism
breaking things down -> usually to get energy
Define Anabolism
Building stuff
Define metabolism
all the reactions in a cell
What are global controls used for?
for if many genes are needed to respond to a single environmental event.
What are two methods for global control
- CAP - Catabolic activator protein
2. Alternative sigma factors
