1. 1 Review What genes control cell differentiation during development Compare and Contrast How is the way Hox genes are expressed in mice similar and different to the way they are expressed in fruit flies 2 Use Analogies Write an analogy that demonstrates how the lac repressor functions 3 A hormone is a chemical that is produced in one part of the body, travels through the blood, and affects another part of the body. Many hormones are proteins. How might the production of a hormone affect the expression of genes in a eukaryotic cell? Write a hypothesis that could be tested to answer this question (include promoters in your hypothesis)

2. Ch 13 RNA and Protein Synthesis
13.4 Gene Regulation and Expression

3. Prokaryotic Gene Regulation
Bacteria and other prokaryotes do not need to transcribe all of their genes at the same time
Saves time and resources
Regulate with DNA binding proteins
Turn genes “on” or “off.”

4. Operons Group of genes that are regulated together
Genes usually have related functions
E. coli have cluster of 3 genes that must be turned on before it can use lactose as food
Lac operon.

5. Promoters and Operators
Promoter (P)
Site where RNA-polymerase can bind to begin transcription
Operator (O)
Where the DNA-binding protein, lac repressor, can bind to DNA.

6. Lac Operon “Off” No lactose present
Lac repressor binds to the O region
RNA polymerase is blocked.

7. Lac Operon “On” Lactose present
Attaches to the lac repressor and changes the shape
New shape makes it fall off the operator
RNA polymerase can bind and transcribe.

8. Eukaryotic Gene Regulation
TATA box
Contains the sequence TATATA or TATAAA
Binds a protein that helps position RNA polymerase.

9. Transcription Factors
DNA-binding proteins
Enhance transcription by opening up tightly packed chromatin, attract RNA polymerase, or block access to certain genes
Attach to RNA polymerase before it binds to DNA.

10. Cell Specialization Many eukaryotes are multicellular
Different cells have very different job but yet all have the same DNA.

11. RNA Interference Small RNA molecules Get transcribed
Not mRNA, rRNA, or tRNA
Get transcribed
Fold over to become double stranded
Enzyme called the “Dicer” enzyme cuts, or dices, these double-stranded loops into microRNA (miRNA)
Two strands separate.

12. RNA Interference miRNA pieces attaches to a cluster of proteins
Forms a silencing complex.

13. RNA Interference Silencing complex binds to complementary mRNA
miRNA sticks to mRNA and stops their protein- making instructions.

14. RNA interference (RNAi)
Blocking gene expression by means of an miRNA silencing complex.

15. The Promise of RNAi Technology
Ability to turn on or off genes
Work with viruses or cure cancer?

16. Genetic Control of Development
As an embryo develops, different sets of genes are regulated by transcription factors and repressors
Gene regulation helps cells undergo specialization.

17. Homeotic Genes
Master control genes that regulate organs that develop in specific parts of the body
Homeobox
Group of the same homeotic genes
Important in cell development and differentiation.

18. Hox genes Determine the identities of each segment of the body
Arranged in the exact order in which they are expressed, from anterior to posterior.

19. Hox genes exist in the DNA of other animals
Tell the cells of the body how to differentiate as the body grows.

21. Environmental Influences
Presence of lactose in E. coli
Bullfrog metamorphosis depends on conditions - a drying pond, a high density of predators, low amounts of food- tadpoles may speed up their metamorphosis.