Genes and Transcription - Genes and Transcription Overview...

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Genes and Transcription Overview This module look at gene structure at the molecular level (in both prokaryotes and eukaryotes), and examines the process of transcription, by which the information encoded in DNA is copied into and RNA messenger. RNA processing, which produces a mature RNA molecule from an initial transcript, will also be considered. Objectives 1. Understand the central dogma of gene expression. 2. Know how genes are defined, and what their basic structure is. 3. Understand the difference between exons and introns in eukaryotic genes. 4. Know the basic structure of regulatory regions of genes (promoters and enhancers), and understand their function. 5. Understand the role of RNA polymerase in transcription, and know the essential steps of transcription. 6. Know the basic differences between prokaryotic and eukaryotic transcription. 7. Understand how eukaryotic RNAs are processed after transcription to produce functional mRNAs. The Central Dogma of Molecular Biology In addition to being able to replicate itself (see DNA replication ), the genetic material must be able to store genetic information, and be able to express that information. How information is stored in DNA will be considered elsewhere (see the module on the Genetic Code ). Expression of the information occurs in the following way: the information coded in the DNA is transmitted to an intermediary molecule, RNA. The information in the RNA is then interpreted and translated into a sequence of amino acids , which makes up a polypeptide . The polypeptide, either on its own or in conjunction with other polypeptides, carries out the function specified by the information in the DNA. This flow of genetic information is represented in the following diagram: This module deals with the process of transcription. A consideration of how the information in RNA is used to produce protein can be found in the modules on the Genetic Code and Translation . Genes Not all of the DNA in a cell has its genetic information transmitted to RNA intermediaries. The regions of DNA that do transmit information to RNA are called genes . A gene, therefore, is defined by the initial RNA molecule that is transcribed from it. In the case of prokaryotes, the initial RNA molecule, or initial transcript , is equivalent to the final mature RNA. Eukaryotic RNAs are another story, however. The initial transcript in most eukaryotic genes is processed so that the mature RNA is significantly different. For example, if you compare the nucleotide
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sequence of the final RNA to the sequence of the gene from which it was transcribed, an interesting property becomes apparent. Nucleotide sequences that are contiguous on the RNA molecule are separated by other nucleotide sequences in the gene. In other words, there are extra nucleotide sequences in the DNA (represented by white areas in the gene) that are not represented in the final RNA molecule, and that "intervene" between the segments of DNA whose sequences are represented in the final
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This note was uploaded on 03/06/2011 for the course BIOL 100B taught by Professor Nargesshassanzadeh-kiabi during the Winter '08 term at California State University Los Angeles .

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Genes and Transcription - Genes and Transcription Overview...

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