35 - MCB 142 Professor Georjana Barnes 11/16/07 Lecture 35...

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Lecture 35 ASUC Lecture Notes Online (formerly Black Lightning) is the only authorized note-taking service at UC Berkeley. Please do not share, copy or illegally distribute these notes. Our non-profit, student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. Sharing or copying these notes is illegal and could end note taking for this course ANNOUNCEMENTS Office Hours next week: Nov 19, Monday, 1-2:30pm 301 Barker Nov 26, Monday 1-2pm 301 barker Nov 28, Wednesday 1-2pm, 301 barker Midterm: Average: 137/150 Standard Deviation: 11 No office hours next Wed. The announcement is in regards to Figure 17-7: during office hours, I realized that there are two issues about this figure. In the textbook, the figure legend is wrong. The description in the text is correct but the legend is wrong. In my slides, though I’ve already corrected this on bSpace, the original labeling of the graph was wrong. What you needed to do in both cases was to put DNA that was lac I+Z+ (input DNA) into a strain that was lac I- Z-. The second exam is back. You can pick it up from the GSIs in the hallways after lecture. EUKARYOTIC GENE REGULATION Review The topic at hand is eukaryotic gene regulation. Last time we were talking about controlling gene expression in eukaryotes and focusing initially on the important step of gene expression, which was controlling transcription. So we’ve been talking about promoter elements, enhancer elements, and these are cis-acting sequences of DNA. They are some kind of sequence of DNA but don’t themselves encode trans-acting factors. We went through promoters and enhancers – these are pieces of DNA that need to be near or connected on the same chromosomes as the coding sequences being regulated. Then we started talking about transcription factors, which are trans-acting. These are usually proteins but can also be small pieces of DNA. They can be coded anywhere in the genome and do not have to be tied physically to coding sequences. Transcription factors can be activating or repressing. For an example of activating transcription factors, we considered Jun-Fos proteins and how they formed homodimers and heterodimers. Then we began looking at repressing transcription factors. Repressors can act in many different ways. Repressors can compete with activators for the binding site and block the activator from binding. There are two parts to the idea that repressors can physically interact with activators; repressor activity can physically bind to activator activity in two different ways: 1) Repressors can bind to the DNA binding domains of activators and physically block the activators’ ability to bind the enhancer region. 2)
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35 - MCB 142 Professor Georjana Barnes 11/16/07 Lecture 35...

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