Agenda 3/16 Eukaryotic Control Introduction and Reading Lactase Gene Regulation Click and Learn Eukaryotic Control Notes Homework 1. Agouti Mice Ted Talk 2. Eukaryotic Control Table Turn in: Video notes, POGIL

Eukaryotes vs. Prokaryotes Eukaryotes have a lot more genes Chromatin is wrapped around histones in eukaryotes (more obstacles to access DNA) More regulatory proteins used in eukaryotes than in prokaryotes

Why do eukaryotes need gene expression control? All cells in our body have the exact same DNA Differences between the cells come from differential gene expression Some genes are turned off in some cells, other genes are turned on Gene expression patterns are regulated at many different levels

Levels of Gene Expression Control in Eukaryotes 1. Pre-transcriptional Methylation Acetylation Transcription Factors 2. Post-transcriptional Alternative splicing 3. Post-translational Ubiquitination

DNA Organization in Eukaryotes In order for transcription to occur, enzymes like RNA polymerase must be able to access the DNA Allowing or restricting that access is one way we can control gene expression Double helix DNA is wrapped around histone proteins

Epigenetics (Pre-transcriptional) Epigenetics (Above the genome) is the process of gene regulation that occurs without changing the underlying sequence of DNA Chemical groups can bind to DNA and make the DNA more likely or less likely to be transcribed (turn genes on or off) Two types 1. Acetylation 2. Methylation

Acetylation (pre-transcriptional) The amino acid lysine in the histone proteins can bind the acetyl groups When acetylation occurs at a lysine, it decreases the affinity of the histone proteins for DNA Meaning the DNA binds less tightly to the histone proteins This makes the DNA more accessible for transcription ‘Gene turned on’ or ‘gene activated’

Methylation (pre-transcriptional) A methyl group can bind the cytosines that are followed by guanine in DNA Methylation makes DNA bind more tightly to the histone proteins DNA is less accessible ‘gene turned off’ or ‘gene deactivated’

Epigenetics and the environment Scientists have found that certain environmental factors affect your epigenome For example, cigarette smoke and stress can create ‘bad epigenetic marks’ Exercise and healthy eating can create ‘good epigenetic marks’ There is some evidence that these epigenetic markers are passed down through generations Meaning, that the choices your grandparents made affect the expression of your genes

Transcription Factors (pre-transcriptional) Transcription factors are proteins that bind to or near the promoter region and help RNA polymerase attach (making transcription more likely) Inducer regions are sequences of DNA that transcription factors may attach to Enhancer regions can by 1000s of nucleotides away but can also bind TFs which can loop back to promoter region and promote transcription

Alternative Splicing (post-transcriptional) Once the immature mRNA is made, it can be processed in different ways which will give rise to different proteins This process is highly regulated and organized by lots of different proteins In one cell, proteins may include an exon in the mRNA but in a different cell it may be spliced out with the introns

Ubiquitination (Post-translational) Ubiquitin is a protein that can ‘tag’ other proteins for destruction Proteins that are tagged with ubiquitin (ubiquitinated) will be degraded in the proteasome