1. Gene Expression

2. Remember, every cell in your body contains the exact same DNA… …so why does a muscle cell have different structure and function than a nerve cell?

3. Review: DNA codes for…

4. Proteins being produced can be turned off and on just like a light switch based on the needs of a cell.

5. Chromosomes Gene 1 Gene 2 Gene 3 Gene 4 Gene 5 Gene 6 A structurally organized single piece of coiled DNA containing many different genes. Each gene will code for ONE single PROTEIN.

6. Regulated Gene Expression Regulated = control the speed/amount Gene Expression = using the information from a gene to express a protein Regulated Gene Expression = how a cell controls the speed or amount of a gene being expressed as a protein

7. Methods of regulation In Eukaryotes: 1. Regulating transcription (DNA  mRNA) by: 1. Activator Proteins 2. Promoters 2. Splicing of mRNA Exons - Expressed In Prokaryotes: 1. Regulating transcription (DNA  mRNA) by: 1. Operators 2. Promoters 3. Repressor Protein

8. Regulation in Eukaryotes #1 Regulating Transcription (DNA  mRNA) If a protein is needed by the cell, a gene coding for that protein needs to be expressed, TRANSCRIPTION WILL OCCUR. If a protein is NOT needed by the cell, TRANSCRIPTION WILL STOP.

9. Eukaryotic Transcription Factors - Activator Protein - a molecule that turns ON transcription - Transcription Factors – molecules that allow RNA Polymerase to bind to DNA and begin transcription - Promoter – sequence on DNA before the Gene where Activator Proteins and Transcription Factors can bind to…

10. Eukaryotic: Transcription will TURN ON When Activators and Transcription Factors are both bound to the Promoter site, RNA polymerase will bind to DNA and begin transcription. The gene will be transcribed and the protein will be translated/expressed.

11. Eukaryotic: Splicing RNA After Transcription: Portions of the transcribed mRNA is (spliced) cut out Exons – the portions of the gene on mRNA that are cut, translated, and EXPRESS proteins Intron – the portions of the gene on mRNA that do not code for proteins and are NOT expressed The spliced Exons will then code for a Protein!

12. Regulation of Prokaryotic Genes Operon – multiple genes that are grouped together on one consecutive segment of DNA that is transcribed/copied onto ONE single mRNA Promoter – sequence in an operon where RNA polymerase binds to and begins transcription Operator – sequence in an operon where a repressor can bind or unbind to Repressor – a protein that can bind to the operator to PREVENT Transcription from occurring

13. Lac Operon - Prokaryotes Lac Operon: a DNA sequence of three genes (Lac Z, Lac Y, & Lac A) that codes for proteins that break down lactose

14. When lactose is present… - Repressor is NOT BOUND to the operator - RNA polymerase can bind to the PROMOTER and TRANSCRIPTION OCCURS - Expression of lactase proteins occurs

15. When lactose is absent… Repressor IS BOUND to the operator RNA polymerase can NOT bind to the PROMOTER and TRANSCRIPTION Does NOT Occur Expression of lactase proteins is REPRESSED! (switch is OFF)