1. Gene Expression (Epigenetics) Chapter 19

2. What you need to know The functions of the three parts of an operon. The role of repressor genes in operons. The impact of DNA methylation and histone acetylation on gene expression. The role of oncogenes, proto- oncogenes, and tumor suppressor genes in cancer.

3. Bacteria Gene Expression: Transcription Operons are clusters of genes in bacteria They can be turned on and off Parts: 1.Operator: an on/off switch for all the genes 2.Promoter: RNA Polymerase attachment site 3.Genes: DNA for each protein in the operon

4. Operons: On/Off Regulatory genes – make repressor proteins that bind to operators and blocks RNA Polymerase (off) Repressible operon – usually on (repressor protein’s off), anabolic, and builds an essential chemical –Turned off by a corepressor which activates the repressor Inducible operon – usually off (repressor protein on) and catabolic –Turned on by an inducer that deactivates the repressor

5. Eukaryotic Gene Expression : Transcription Nucleosomes are DNA tightly wrapped around histones DNA methylation – the addition of methyl groups to DNA making genes less accessible Histone Acetylation – acetyl groups are added to histones to loosen DNA http://teach.genetics.utah.edu/conte nt/epigenetics/http://teach.genetics.utah.edu/conte nt/epigenetics/

6. Eukaryotic Gene Expression : Transcription Transcription initiation complexes also regulate gene expression Enhancer region upstream from the gene is joined to the transcription initiation complex by activators (proteins) = start transcription http://www.dnai.org/a/index.html

7. Eukaryotic Gene Expression : preTranslation Tiny single strand RNA molecules can block mRNA –micro RNA – miRNA –small interfering RNA – siRNA They will degrade the mRNA or block its translation

8. Cell Specialization Cell differentiation is the process by which cells become specialized –Muscle tissue, neural tissue, etc. As the zygote grows and divides (mitosis) it begins morphogenesis (organization of cells into tissues)

9. Morphogenesis 1.Cytoplasmic determinants are maternal substances in the egg that influence early development (uneven in early cells) 2.Cell-cell signals are molecules made by cells (external hormones) that influence other cells (induction) –Determination is the series of events that lead to cell differentiation Pattern formation sets up the body plan (head/tail, left/right, etc.) and is impacted by both

10. Cancer Proto-oncogenes are healthy genes that promote cell growth Mutation of these genes creates oncogenes Oncogenes are overstimulated proto-oncogenes that cause cancer Tumor-suppressor genes inhibit cell division (mutations here can also cause cancer)

11. Tumor-Suppressor: p53 Three types of suppression: 1.Binds to cyclin-dependent kinases – halts division until DNA can be repaired 2.Turns on DNA repairing genes 3.Triggers apoptosis when DNA damage is too great