Intro to Gene Regulation 1 Organisms have lots

Gene regulation continued • Prokaryotes: respond rapidly to environment – Transcription and translation are

On/off, up/down, together • Sometimes genes are off completely and never transcribed again; some

How is gene expression controlled? 4 1. Transcription: most common step in control. •

Gene regulation (cont. ) 5 1. Translation: prokaryotes, stops transcrp. early. 2. Stability of

Slides: 5

Intro to Gene Regulation 1 • Organisms have lots of genetic information, but they don’t necessarily want to use all of it (or use it fully) at one particular time. • Eukaryotes: Development, differentiation, and homeostasis – In going from zygote to fetus, e. g. , many genes are used that are then turned off. – Liver cells, brain cells, use only certain genes – Cells respond to internal, external signals

Gene regulation continued • Prokaryotes: respond rapidly to environment – Transcription and translation are expensive • Each nucleotide = 2 ATP in transcription • Several GTP/ATP per amino acid in translation • If protein is not needed, don’t waste energy! – Changes in food availability, environmental conditions lead to differential gene expression • Degradation genes turned on to use C source • Bacteria respond to surfaces, new flagella etc. • Quorum sensing: sufficient # of individuals turns on genes. 2

On/off, up/down, together • Sometimes genes are off completely and never transcribed again; some are just turned up or down – Eukaryotic genes typically turned up and down a little compared to huge increases for prokaryotes. • Genes that are “on” all the time = Constitutive • Many genes can be regulated “coordinately” – Eukaryotes: genes may be scattered about, turned up or down by competing signals. – Prokaryotes: genes often grouped in operons, several genes transcribed together in 1 m. RNA. 3

How is gene expression controlled? 4 1. Transcription: most common step in control. • Control at promoter area 2. RNA processing: only in eukaryotes. • Alternate splicing changes type/amount of protein. 3. RNA interference • Small interfering RNAs cause m. RNA destruction

Gene regulation (cont. ) 5 1. Translation: prokaryotes, stops transcrp. early. 2. Stability of m. RNA: longer lived, more product. 3. Post-translational: change protein after it’s made. Process precursor or add PO 4 group. 4. DNA rearrangements. Genes change position relative to promoters, or exons shuffled.