1. Transcription Initiation:
Specific transcription factors (activators or repressors) bind to control elements (enhancer region)
Activators: increase transcription
Repressors: decrease transcription

2. Transcription Initiation Complex
Activators bind to enhancer regions + other proteins
+ RNA polymerase

3. Cell type-specific transcription

4. Regulation of mRNA:
micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation

6. Summary of Eukaryotic Gene Expression

10. Video: The Epigenetics of Identical Twins
Genetic Science Learning Center

11. Embryonic Development of Multicellular Organisms
Section 18.4

12. Embryonic Development: Zygote  Organism
Cell Division: large # identical cells through mitosis
Cell Differentiation: cells become specialized in structure & function
Morphogenesis: “creation of form” – gives organism’s shape

13. Determination: irreversible series of events that lead to cell differentiation

14. Cytoplasmic determinants: maternal substances in egg distributed unevenly in early cells of embryo

15. Induction: cells triggered to differentiate
Cell-Cell Signals: molecules produced by one cell influences neighboring cells
Eg. Growth factors
Induction: cells triggered to differentiate

16. Pattern formation: setting up the body plan (head, tail, L/R, back, front)

17. Morphogens: substances that establish an embryo’s axes

18. Homeotic genes: master control genes that control pattern formation (eg. Hox genes)

19. Evolving Switches, Evolving Bodies
HHMI Short Film

20. Pitx1 Gene = Homeotic/Hox Gene
Stickleback Fish
Humans
Development of pelvic bone
Development of anterior structures, brain, structure of hindlimb
Mutation may cause clubfoot, polydactyly (extra fingers/toes), upper limb deformities

21. Role of Apoptosis Most of the embryonic cells are produced in excess
Cells will undergo apoptosis (programmed cell death) to sculpture organs and tissues

22. Cancer results from genetic changes that affect cell cycle control
Section 18.5

23. Control of Cell Cycle: Proto-oncogene = stimulates cell division
Tumor-suppressor gene = inhibits cell division
Mutations in these genes can lead to cancer

24. Proto-Oncogene Oncogene
Gene that stimulates normal cell growth & division
Mutation in proto-oncogene
Cancer-causing gene
Effects:
Increase product of proto-oncogene
Increase activity of each protein molecule produced by gene

25. Proto-oncogene  Oncogene

26. Genes involved in cancer:
Ras gene: stimulates cell cycle (proto-oncogene)
Mutations of ras occurs in 30% of cancers
p53 gene: tumor-suppressor gene
Normal anti-cancer functions:
Activate p21 gene, whose product halts cell cycle for DNA repair
Activate miRNAs to inhibit cell cycle
turn on DNA repair genes
activate apoptosis (cell suicide) if DNA repair not possible
Mutations of p53 in 50+% of cancers

27. Cancer results when mutations accumulate (5-7 changes in DNA)
Active oncogenes + loss of tumor-suppressor genes
The longer we live, the more likely that cancer might develop

30. Summary
Embryonic development occurs when gene regulation proceeds correctly
Cancer occurs when gene regulation goes awry