1. Regulation of Gene Activity

2. Conservation Remember, our bodies are conservative, they only make what we need, when we need it. How do they know this???

3. Operon Jacob and Monod – E. coli – capable of regulating the expression of its genes Regulator gene – codes for repressor Repressor – controls whether the operon is active or not.

4. Operon Promoter - DNA, beginning of gene to be transcribed, signals the start of a gene Operator – portion of DNA where repressor binds, controls mRNA synthesis  When repressor binds here, RNA polymerase cannot attach to the promoter, prevents transcription Structural genes – codes for primary structure of enzyme to be transcribed.

5. trp operon Exist in “on” position – repressible Products – 5 different enzymes, synthesis of AA tryptophan If tryptophan is already present, it binds to repressor, which then binds to operator and no transcription takes place.

6. lac operon Makes 3 enzymes needed for metabolism of lactose When lactose is present, it binds to the repressor, and repressor cannot bind to operator, therefore transcription takes place Lactose is an inducer, inducible operon

7. Eukaryotic regulation 5 primary levels of control Chromatin structure Transcriptional control: transcriptional factors initiate/regulate transcription Posttranscriptional control: mRNA processing and how fast mRNA leaves the nucleus Translational control: when translation begins and how long it continues Posttranslational control: after protein synthesis, polypeptide may have to undergo additional changes before it is functional.

8. Chromatin structure Levels of chromatin organization is related to the degree that the nucleosomes coil. Heterochromatin – highly condensed chromatin, inactive  Barr Body- only in females, small, dark, condensed chromatin, inactive X chromosome Euchromatin – loosely compacted chromatin, potentially active, genes expressed.

9. Genetic mutations Point mutations – change in a single DNA nucleotide, change in specific codon Frameshift muations – one or more nucleotides are inserted or deleted Nonfunctional proteins – can have dramatic effects on phenotype

10. carcinogenesis When proto-oncogenes mutate, they become oncogenes. Tumor suppressor genes usually act to stop cell division if there is a problem. Cancer – loss of TSG and activity of oncogene = uncontrollable cell division