key_inheritance_addnl_problems2

key_inheritance_addnl_problems2 - Inheritance Additional...

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Inheritance – Additional problems. Bis2A / Gerhart. 1. When a protein binds to the DNA and stops transcription of a gene, it is called negative control of the gene (or operon). When a protein binds to the DNA and increases the transcription of a gene, it is called positive control of the gene (or operon). A. What type of control does the repressor protein cause in the lac operon (this is the protein that binds to the DNA and blocks RNA polymerase)? B. What type of control does the CRP protein cause in the lac operon (this is the protein that binds to the DNA and stabilizes binding of RNA polymerase)? The repressor protein binds to the DNA and stops RNA polymerase from transcribing the gene or operon – this is an example of negative control. The CRP protein binds to the DNA and makes it so that RNA polymerase is able to bind to the promoter and read the gene(s) – this increases rate of transcription (by 50- fold, from near-zero to high rates of mRNA production in the case of the lac operon) and is an example of positive control. 2. What need does the lac operon sense before becoming active? What material is necessary for the lac operon to work (that is, what other thing must be sensed before the genes are transcribed)? What do the genes of the lac operon actually do, to help the cell address this need? The “need” sensed is inadequate fuel – if the cell is low on fuel, then it will produce cAMP (a cyclic, mono-phosphate derivative of ATP) to signal that it is low on energy. The lac operon senses this need via the CRP protein
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This note was uploaded on 07/03/2009 for the course BIS 64982 taught by Professor Comai during the Spring '09 term at UC Davis.

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key_inheritance_addnl_problems2 - Inheritance Additional...

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