1. Control of Gene Expression Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.

2. Essential Knowledge • 3B1: Gene regulation results in differential gene expression, leading to cell specialization. • 3B2: A variety of intercellular and intracellular signal transmissions mediate gene expression

3. Much Diversity due to Gene Expression • Each tissue in our body is very different despite having the same DNA • Even identical twins have many differences due to gene expression

4. Some Basics: Regulatory Sequences • Stretches of DNA that interact w/ regulatory proteins to control transcription. • Allows RNA Polymerase to bind on. • AKA promoter (TATA box) • Enhancers are sequences that increase transcription

5. Some Basics: Regulatory Genes • Code for proteins or mRNAs which affect gene expression • Ex: microRNAs • Repressor proteins • Transcription factors/ enhancers

7. Some Basics: Operons • Simple gene expression mechanisms in prokaryotes

8. Components of the Operon • Operator, sequence next to the promoter (On/Off switch) If repressor protein is on it, then off…can’t make genes • Promoter (where RNA polymerase binds) • Genes that work together

9. Types of Operons • Some genes are normally “off” and can be turned “on” Presence of a molecule induces gene expression or enhancesgene expression • Some genes are normally “on” and can be turned “off”  Presence of a molecule represses gene expression

10. Inducing Gene Expression: Lac Operon, + Control • If lactose present, bacteria need to make lactase to break it down. • Lactose binds to repressor on operator  repressor is released from operator • RNA polymerase now fits onto promoter region to make mRNA  protein lactase.

11. Negative ControlCase Study: Trp Operon • Tryptophan fits in repressor  blocks RNA polymerase. • Once out of tryp, repressor changes shape to allow promoter available to make more tryptophan  turns transcription on.

12. Ribosomal Genes… • Always on!!! Always Expressed!

13. In Eukaryotes… • No operons… • Gene expression involves regulatory genes, regulatory elements, and transcription factors.  All work together to determine how much product is made.

14. Transcription Factors • Bind to specific DNA sequences • Some activate (increase expression) and some are repressors (decrease expression)

15. Signal Transmission • Within and b/t cells mediates gene expression. • Ex: cytokines regulate gene expression to allow cell replication and division.

16. Signal Transmission • Within and b/t cells mediates cell function. • Ex: HOX genes (homeotic genes)

17. Mr Anderson • http://www.youtube.com/watch?v=3S3ZOmleAj0

18. Lac Operon or Trp Operon Flow Map