AP Bio - Unit 6: Gene Expression and BioTechnology (Gene Regulation)

Why is gene regulation necessary?

Why is gene regulation necessary?

allows for specialized cells, maintains homeostasis

regulation in prokaryotes

Operon system

operon

genes that are regulated together and are controlled by a switch-like mechanism to respond to internal/external stimuli. two types are inducible and repressable. remember PROG

P - promoter region

R - Regulatory gene

O - Operator gene

G - Gene (targeted)

inducible operon

default setting is off e.g. Lac Operon (turns on gene that makes lactose)

how do inducible operons work (lac operon example)

regulatory gene makes a repressor protein that binds to the operator gene. when an inducer molecule (in this case, lactose sugar) binds to the allosteric site on the repressor protein, it causes a conformational change and it detaches from the operator gene. this allows the RNA polymerase to find the promoter region and transcribe the target gene (in this case lactose)

repressable operon

default setting is on e.g. trp operon (allows for creation of tryptophan)

how do repressable operons work (trp operon example)

regulatory gene makes a repressor protein that is unable to bind to the operator gene. RNA polymerase transcribes the target gene until a co-repressor molecule (in this case, tryptophan) binds to the allosteric site on the repressor protein, it causes a conformational change and it allows for the repressor to bind to the operator gene. this stops the RNA polymerase from transcribing the target gene, turning it “off”.

gene regulation in eukaryotes

few species have operon systems. there are many components/’checkpoints’ to ensure no mistakes are made

how does gene regulation in eukaryotes work

the DNA has a regulatory/enhancer gene, and promoter region and a target gene. attached to the enhancer gene is an activator protein. a protein called the transcription factor protein (tfp) finds the promoter region on the DNA. the DNA then folds, using another protein called the mediator protein to connect the activator protein and the TFP. all together, these proteins make up the transcription factor complex. only once they are all connected can the RNA polymerase transcribe the DNA.

what is a teratoma

a type of tumor when a body cant regulate gene expression