#operons

TA 1: level 0 of gene expression is like if the gene is gone

Before diving into this topic, make sure you understand:

Transcription=process of turning DNA into mRNA

Transcription requires Initiation step, which is when the RNA polymerase binds to a promoter which allows the DNA strand to unfold and begin to be trasncribed

Basically, the RNA polymerase is like your wallet: it gives you an okay on whether or not you can purchase something or not. If the moneys there, you're probably going to spend it. If it's not, there's no possible way you can.

Operons are a set of genes that control expression of genes (discovered by Jacob and Monod).

Lac/Inducible operon: switched off until turned on; can be distracted by allolactose, which prevents RNA polymerase from binding to a promoter (instead the allolactose is) 

Tryptophan/repressible operon: always on until repressed; when binded with prevents RNA polymerase from binding to a promoter

Basically, lac operon is an empty wallet that can have fake money in it. Tryptophan operon is a full wallet of a prudent person

Allosteric proteins play a part in both operons by acting as regulatory genes

Noncoding RNAs also control gene expression

microRNA (miRNA) blocks translation and degrades mRNA

RNA interference (RNAi) turns off genes with matching sequences

RNA=those pesky little things you have to pay for that add up

Onco-genes lead to cancer

Proto onco-genes are proteins that stimulate cell growth and division; too much leads to too much

tumor-suppressor genes lead to uncontrolled cell growth; too much leads to too much

Think of when you eat too much food, you just keep on going and going... 

Usually found in prokaryotic cells.

Remember PROG 

Promoter

Repressor

operator 

genes

Promoter is where the RNA polymerase would attach to created the desired protein

The repressor is what stops the RNA polymerase from creating too much enzyme and fits into the operator physically inhibiting the RNA polymerase. The repressor must be fit with whatever it needs to break down or what it needs to stop creating. 

EX: metabolization of lactose: lactose must be present to fit into and remove the repressor from the operator in order to allow the creation of The LAC enzymes [called the lac operon]

On the flip side some cells need tryptophan, an amino acid, and RNA polymerase makes tryp until tryp fits into the repressor and then attaches it to the operator to stop the reaction

think of the operator like an on off switch