Welcome  In your journal write a paragraph explain what is a gene and what is gene expression?  Notes on Gene Expression Regulation  Quiz over DNA, RNA and Protein Synthesis  HF: None but you need to finish your project this weekends, due next class!

Gene Regulation and Expression

Gene Regulation

Gene Regulation: 1. Modification of Genome (DNA) Chemical factors can structurally change the DNA, turning it on or off. –Chemical processes: DNA methylation & histone modification –Epigenome Gene regulation at the DNA level happens in eukaryotes and rarely, if ever, in prokaryotes.

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Gene Regulation: 2. Transcriptional Regulation Transcriptional factors (regulatory proteins) turn transcription on and off or increase and decrease. This mechanisms happens in eukaryotes and prokaryotes.

Prokaryotic Gene Regulation DNA-binding proteins in prokaryotes regulate genes by controlling transcription. One of the keys to gene transcription in bacteria is the organization of genes into operons.

Prokaryotes : Transcriptional Regulation Operon – functioning unit of DNA containing the following: –A set of genes (DNA the codes for mRNA) –Regulatory sections (DNA that controls the expression of the gene)

Prokaryotes: Transcriptional Regulation

The Lac Operon When lactose is not present, the lac genes are turned off by regulatory proteins that bind to DNA and block transcription.

The Lac Repressor Blocks Transcription When the lac repressor binds to the O region, RNA polymerase cannot reach the lac genes to begin transcription. Repressor protein

Lactose Turns On the Operon When lactose is added to the medium, it diffuses into the cell and attaches to the lac repressor. Lactose Repressor protein with changed shape RNA polymerase

Eukaryote: Transcriptional Regulation Much more complicated and involves: –Many regulatory proteins (transcription factors) –Enhancers and TATA Box

Eukaryote : Transcriptional Regulation

Gene Regulation

One gene can result in several different proteins through a process called:Alternate mRNA Splicing

Cell Specialization Complex gene regulation in eukaryotes is what makes differentiation and specialization possible.

Genetic Control of Development Regulating gene expression is important in shaping how a multicellular organism develops. Each of the specialized cell types found in the adult originates from the same fertilized egg cell.

Homeotic, Homeobox, and Hox Genes  Homeotic genes regulate organ development.  Homeobox genes code for transcription factors.  Hox genes determine the identities of each body segment.

Environmental Influences Environmental factors can affect gene regulation. Metamorphosis is an example of how organisms can regulate gene expression in response to change in their environment.

Check for understanding 1.Draw gene regulation flow map in your journal 2.What is gene expression and how gene expression are regulated (be sure to include modification of DNA, transcriptional regulation, and post-transcriptional regulation) 3.Explain how does a gene turn on, and how does it turn off. You can use lactose gene as an example for your discussion.