Chapter 16: Control of Gene Expression and Epigenetics

what is the reason for controlling gene expression in eukaryotes vs prokaryotes?

prokaryotes: save energy and resources

eukaryotes: cell differentiation and function

points of control of gene expression in eukaryotes vs. prokaryotes

prokaryotes: less points of control

eukaryotes: more points of control

What mechanism do prokaryotes mainly use to regulate gene expression?

transcriptional regulation

operons

units of transcriptional regulation in prokaryotes, all or none of the genes are transcribed

what are operons for?

structural genes: enzymes and cytoskeletal proteins

how are operons regulated?

repressor or activator proteins

negative regulation

binding of repressor proteins prevents transcription

positive regulation

an activator protein binds DNA to stimulate transcription

example of prokaryotic inducible operon

the lac operon in E. coli

inducible operon

regulated by repressor protein

transcription begins from inducer (ex. lactose in lac operon)

substrate in lac operon

lactose

describe the process of the lac operon getting transcribed

• lactose enters

• transglycosylated into allolactose

• allolactose binds to repressor

• repressor cannot bind to DNA

• all genes in lac operon are transcribed

Parts of Operon Purpose: CAP site, promoter, operator

CAP site: activator protein binds

promoter: where RNA polymerase binds

operator: where repressor protein binds

what happens in the lac operon where there