Genetics Notes test 2 - Genetics(for test 2 Lecture 1 DNA...

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Genetics (for test 2) Lecture 1 – DNA RNA = transcription RNA protein = translation Protein phenotype = expression Regulating Gene Expression Can possibly regulate RNA protein or DNA RNA ---probably cannot regulate gene expression by regulating replication because its not specific unless you want all genes regulated. Most popular place = DNA RNA – regulating transcription Operon = (for bacteria) – a series of genes whose expression is co-regulated by regulating expression of their common mRNA Eukaryotes do not use this way to do it. To start transcription, you need a promoter. Promoters can vary from the set sequence (TATATAAT, etc) but the set sequence is the average. Ways transcription can be regulated -Negative Control: “good” promoter – transcription is always on and regulation is used to find a way to turn it down/off. Its always on unless a negative regulatory protein binds to the operator (O) to block RNA polymerase at the promoter (P) -Positive Control: “bad” promoter – transcription is always off unless we figure out a way to crank it on. Its always off unless a positive regulatory protein binds to the operator (O) to help RNA polymerase at the promoter (P) Inducer = molecule from outside (signal) which binds to the regulatory protein. It is a chemical signal from the outside, so obviously no genes code for it.
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Operon: P R = promoter for the R gene that codes for the regulatory protein R = R gene P = promoter O = operator RNA pol Structural Genes DNA P R R P O A B C D a b c d mRNA Regulatory protein gets info for structural genes function is to bind to the sequence near and eventually the proteins promoter called operator site Structural genes code for whatever enzymes or proteins used to carry out a particular pathway. The control is independent of whether the inducer makes the regulatory protein better or worse at binding to the operator. Action of the inducer does not change control, it can only modify/activate action of the regulatory protein. - Synthetic operon – biosynthetic pathway being regulated – outcome of pathway being expressed makes something for the cell - Degredative operon – when pathway is functional, degredation/metabolism of something like food happens Specific Operon Example Lactose operon (lac operon) - its purpose is to control metabolism of a class of sugars (lactose and other betagalactosides sugars) – It is a degredative operon, and there are three structural genes for this operon
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Lac I regulatory protein is expressed from the I gene (P I as promoter), and binds to the operator and stops binding of RNA polymerase to the promoter. It is an example of negative control. The inducer is lactose or another betagalactoside sugar. Z gene – codes for betagalactosidase, the enzyme that allows for the following reaction to occur: lactose (betagalactosidase) glucose + galactose Y gene – codes for a permease, which transports lactose/other sugars into the cell from outside the cell A gene – codes for transacetylase (?) – it is not necessarily needed to metabolize lactose
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