1. Gene Regulation

2. Prokaryote Gene Regulation
Gene regulation  the ability of an organism to control which genes are transcribed is response to the environment
Controlled by an “operon”

3. What is an operon?
Section of DNA that contains the genes for the proteins needed for a specific metabolic pathway
Made of operator, promoter, regulatory gene, and the genes coding for proteins

4. Operator  On/off switch for transcription
Promoter  binding site of RNA polymerase

5. Trp operon
Tryptophan synthesis  5 steps – each catalyzed by a specific enzyme
5 genes coding for these enzymes are clustered together on the chromosome with a group of DNA that controls whether or not they are transcribed

6. Trp operon
Repressible operon because transcription is normally turned off
Turned on only when tryptophan levels are low and synthesis is necessary

7. Lac operon – Inducible operon
3 enzymes that control lactose digestion
Inducer  allolactose – present in food that contains lactose
Binds to repressor gene and inactivates it so transcription can begin

8. Eukaryote Gene Regulation
Requires more than a single promoter and operator for gene regulation
Transcription factors  ensure that a gene is used at the right time and that proteins are made in the right amounts

9. 2 types of transcription factors
Forms complexes that guide and stabilize the binding of the RNA polymerase to a promoter
Controls the rate of transcription

10. Hox Genes Determine the body plan of an organism
Controls differentiation (cells become specialized in structure and function)
Code for transcription factors and are in the same order on the chromosome as they are in the embryo

11. RNA interference
Small pieces of double stranded RNA in the cytoplasm are cut by an enzyme called a dicer
Binds to a protein complex – one strand is degraded
Binds to sequence specific sections on mRNA in the cytoplasm preventing translation