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Chapter 13 Blog: Gene Regulation (Ambika)

Page history last edited by Ambika Sharma 13 years, 5 months ago

In the first section of this page, you will write a daily summary of that day's class.  For example in  your chapter 2 blog, your first entry should be titled 9/3/10.  You should then write a one or two paragraph summary of that day's lecture, outlining the major points.  In the second section, you are required to add two items (link to a website, video, animation, student-created slide show, student-created PowerPoint presentation) and one journal article pertaining to a topic in this chapter.  A one-paragraph summary must accompany each item describing the main idea and how it applies to the lecture topic.  Please see the PBWorks help guide for assistance embedding video and other items directly in the page.  I will also produce a how-to video on using tables to wrap text around items and other useful tips.  Please see the syllabus for organization and grading details.


A.  Daily Blog


     Chapter 13 focuses on GENE REGULATION. Gene regulation refers to the ability of cells to control their level of gene expression. The majority of genes are regulated so that proteins are produced at a certain time and in a specific amount. Two major benefits come from gene regulation: energy is conserved, and genes are expressed in appropriate cell type at the correct stage development. Gene regulation can occur in prokaryotes as well as, eukaryotes. Thus the reason why this chapter was split up into two parts: Gene regulation in prokaryotes and Gene regulation in eukaryotes.

     Let's cover gene regulation in prokaryotes first. Gene regulation in a prokaryotic cell is relatively simple. The operator and the promoter, which are both located upstream, control the operon. The function of the promoter is to provide a binding site for RNA polymerase while the function of the operator is to have an area where activators and repressors can chill. Activators and repressors are transcriptional factors that pretty much determine whether or not transcription can occur. Activators are the "on" switch, they "turn on" transcription while repressors are the "off" switches and "turn off" transcription. Transcriptional factors are proteins that bind to DNA in the vicinity of a promoter and affect the rate of transcription of one or more nearby genes. A great example from our textbook for gene regulation in prokaryotes is the regulation of lactose breakdown in E. Coli. This process is controlled by the lac operon, which consists of three adjacent structural genes: lacZ, lacY and lacA. The whole base of this process is "How much glucose is present?" and "Is lactose present?" Is lactose is not present, repressors bind to the promoter. This INHIBITS transcription. However, if lactose is present, the repressors are silences and RNA polymerase can attach. Thus, transcription can occur depending on the absence or presence of glucose. If glucose is absent, cAMP is high. The best environment for a lac operon for transcription to occur is: high levels of lactose and low levels of glucose.

     Now let's focus on gene regulation in eukaryotes! Gene regulation is eukaryotic cells are said to be a lot more complicated. Eukaryotic cells are regulated by small effecter molecules but they lack operons. Why? This is because the genes are regulated individually and and expressed differently depending on the cell type. Eukaryotic genes are controlled by combinatorial control. This means that the gene expression is not just "on" or "off" but instead, there are different levels of the rate of gene expression. The promoters of eukaryotic cells are different too! Eukaryotic cell promoters consist of three main componenets: the TATA box, a transcriptional start site and regulatory factors. In order for transcription to begin, all three of these components must be active. The TATA box is composed of "T" and "A": thymine and adenine nucleotide bases. The TATA box is where RNA polymerase binds. The regulatory factors are made up of enhancers and silencers: enhancers "enhance" transcription, while silencers "silence" (decrease) transcription. Proteins, like the mediators, activator and repressor proteins, greatly affect the rate of translation. 


B.  Useful Materials


Useful Video
YouTube plugin error   This is a great video that focuses on the lac operon. The E. coli lac operon contains the genes for the enzymes that allow it to metabolize lactose. It is an example of an inducible set of genes. More specifically, this video focuses on two of the three lac operon genes. These genes are protease and β-galactosidase. These genes are responsible for the breakdown of lactose into sugars used for cellular metabolism. I hope this video helps! 


Useful Link  
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Promoter.html   This is a site that I found very helpful. It mostly focuses on gene regulaton of eukaryotic cells. Personally, I liked the layout of it and how everything that was described was concise but informative. It may seem like a bunch of words but don't be scared, there are a few pictures... Check it out!! 


Useful Article

OPERating ON chromatin, a colorful language where context matters.


This is an interesting article. It focuses on how histones, which are the fundamental packaging elements of eukaryotic DNA, are highly decorated with a diverse set of post-translational modifications. Just as a quick reminder, the function of post-translational modifications are to overlook the structure and function of chromatin. The article references back to how ten years ago, when the histone code hypothesis was formulated, there was very limited understanding of the post-translational modifications on histones and the protein that interpret them. There is still debate over whether or not histone post-translational modifications follow a "strict code". However, scientists have come to the realization that these post-translational modifications really do play a huge part in regulation of activities associated with chromatin. Hopefully, we can learn more about these post-translational proteins in the near future!




Comments (1)

Derek Weber said

at 12:40 am on Feb 16, 2011

Nice job overall. The items section is well organized.

Use the learning objectives as a guide for your chapter summary so you don't miss any important material.

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