1. G ENE R EGULATION

2. H OW DOES A CELL KNOW ? which gene to EXPRESS & which gene should stay SILENT?

3. G ENE R EGULATION When a gene is EXPRESSED, it is transcribed into mRNA. When a gene is SILEN T, it is NOT transcribed. EXPRESSED GENE = TRANSCRIBED SILENT GENE = NOT TRANSCRIBED

4. G ENE R EGULATION Why would a cell NOT want to express a gene? – Wastes energy & materials ATP

5. G ENE R EGULATION Cells regulate what genes are expressed based on what protein the cell NEEDS.

6. G ENE R EGULATION Where does regulation occur? At what step? Most regulation occurs at the DNA to RNA step—transcription! Why? Conserves the most energy!

7. G ENE R EGULATION —H OW ? Expression is regulated by: Promoters Start & Stop Base Pair Sequences Regulatory Sites called Operators

8. G ENE R EGULATION --P ROMOTERS What is a promoter? Specific DNA base pair sequence that provides a binding site for RNA polymerase. “Promotes” or allows transcription to occur

9. G ENE R EGULATION -S TART AND S TOP B ASE P AIR S EQUENCES What do they do? Control where transcription starts and stops. If changed (mutated), transcription is altered. AUG UAA UAG UGA

10. G ENE R EGULATION -O PERATORS What is an operator? Like an on/off switch. Proteins bind to the operator to regulate transcription.

11. G ENE R EGULATION -R EPRESSORS What is a repressor protein? Binds to the operator to physically blocks the RNA polymerase from the promoter site. BINDS HERE BLOCKS THE PROMOTER

12. G ENE R EGULATION -E NHANCERS What is an enhancer protein? Binds to the operator to enhance binding of the RNA polymerase to the promoter site. BINDS HERE ENHANCES BINDING TO THE PROMOTER

13. G ENE R EGULATION IS DIFFERENT IN P ROKARYOTES AND E UKARYOTES, WHY ? Discuss with the person next to you. Prokaryotic DNAEukaryotic DNA

14. P ROKARYOTIC G ENE R EGULATION In prokaryotes, genes are organized into operons. What is an operon ? A group of genes that code for the same function, and are regulated by the same promoter and operator. One promoter/operator controls the expression of multiple genes.

15. E UKARYOTIC G ENE R EGULATION Eukaryotic DNA has exons and introns. What are exons? The coding regions of DNA that are expressed into proteins. What are introns? Non-coding regions of the DNA.

16. E UKARYOTIC G ENE R EGULATION

18. C ELL D IFFERENTIATION

19. One chromosome may have several genes. Not all the genes will be transcribed and translated. The genes that are transcribed and translated determine the type of cell.

20. C ELL D IFFERENTIATION So these cells all have the exact same DNA, but each cell uses different segments of the DNA during transcription.