Presentation is loading. Please wait.

Presentation is loading. Please wait.

Why genes are regulated

Similar presentations

Presentation on theme: "Why genes are regulated"— Presentation transcript:

1 Why genes are regulated
Organisms respond to environment - e.g. nutrients available Multi-cellular organisms must have different cell types (differentiation) Genes must be switched on/off at correct times and in correct cells Gene regulation is complex and precisely controlled process

2 DNA does not change All cells in an organism have the same set of genes (usually) DNA sequence does not change but genes can be switched on/off Gene regulation must be a reversible process Some gene activities are required in all cell types (housekeeping genes) e.g. synthesis of RNA Others are tissue specific e.g. to make muscle proteins (myosin, actin) in muscle cells

3 Any cell has all genes to make frog
Adult frog Unfertilised egg Skin cell removed and cultured Destroy nucleus by UV light Nucleus removed and micro-injected into egg Normal embryo Normal tadpole

4 Regulation at what stage?
DNA RNA Protein Transport, Processing transcription translation Active protein Several places at which regulation could occur Mostly regulated at transcription stage Most economical - don’t make things that aren’t needed Achieved by specific proteins that bind to DNA

5 DNA binding proteins Specific proteins bind to specific points in the DNA The two fit together like a lock and key Almost all genes are regulated this way DNA Protein

6 Gene regulation in bacteria
Simple systems to turn genes on and off Response to nutrients e.g. if tryptophan (an amino acid) is in the medium, don’t need to make your own Similar systems exist for other amino acids Turning a gene off is repression

7 Tryptophan (trp) gene regulation
Trp operon promoter E D C B A trp synthesis enzymes DNA RNA No trp Trp present Repressor protein RNA polymerase No transcription

8 Gene activation Bacteria turn on genes to use sugars for energy when available Turning genes on is activation Also uses specific DNA-binding proteins protein DNA RNA RNA polymerase Activator Environmental stimulus Promoter

9 Gene regulation in eukaryotes
Genes have to be switched on by regulatory proteins, otherwise would do nothing General proteins in all cell types, special ones in specific cell types Regulatory proteins bind to sites in DNA called enhancers Enhancers can be 1000s of bp away from gene

10 Gene regulation in eukaryotes
Specific activator protein Promoter Enhancer RNA polymerase & general transcription factors

11 Drosophila eye development
Cells for eye Cells for leg Larva Adult Normal Ey gene artificially expressed in cells for leg “Eye” on leg

Download ppt "Why genes are regulated"

Similar presentations

Ads by Google