Regulation of Gene Expression

transcription

transcription

RNA polymerase READS template strand in 3’ to 5’ direction; SYNTHESIZES RNA in 5’ to 3’ direction

translation

ribosomes reads mRNA, moves towards 3’ end one codon at a time

gene regulation

ability of cells to control level of gene expression

why are genes regulated?

to ensure gene products are produced at the correct time and in the appropriate amount to save energy

constitutive genes

essential genes that have constant levels of expression

where does gene regulation occur in eukaryotes?

transcription, RNA processing, translation, post-translation

cell differentiation

producing different cell types in multicellular organisms that is dependent on regulating gene expression

hemoglobin in fetal vs. adult humans

• fetal has higher oxygen affinity than adult

bacterial gene regulation

occurs on multiple levels, but transcriptional is the most common

why is gene regulation triggered in prokaryotes?

to respond to changes in the local environment

when will E. Coli utilize lactose?

when no glucose is present

when are enzymes that metabolize lactose expressed?

when lactose is present

lactose permease

transports lactose into the cell (PERMits it to enter)

B-galactosidase

breaks down lactose (B for Break)

regulatory transcription factors

proteins that bind to regulatory sequences in DNA

repressors

inhibit transcription (negative control)

activators

increase rate of transcription (positive control)

two domains in a regulatory transcription factor

1. site where protein binds to DNA

2. site specifically for small effector molecules

small effector molecule

binds to regulatory transcription factor, causes conformational change to either have it bind or not bind to DNA

operator

regulatory region of operation, downstream of promoter

polycistronic mRNA

group of genes with a common function; entire operon is transcribed