Lecture 34-Gene Regulation

Lecture 34-Gene Regulation - Lecture 34- Gene Regulation...

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Lecture 34- Gene Regulation Transcription and Translation -In prokaryotes, RNA polymerase synthesises an mRNA molecule that is ready for translation on ribosomes -In eukaryotes, RNA polymerase synthesises a precursor-mRNA (a pre-mRNA molecule) that has extra segments that are removed by RNA processing to produce a translatable mRNA. that mRNA exist the nucleus through a nuclear pore and is translated on ribosomes in the cytoplasm -Because of the nuclear membrane in eukaryotes, the transcript is protected from the cytoplasm, therefore eukaryotes have a tremendous opportunity for the regulation of gene expression Transcription -Only one of the two DNA strands is used as a template for synthesis of the complimentary RNA transcript 1) An RNA polymerase molecule binds to the RNA at the beginning of the gene to be transcribed 2) The DNA begins to unwind at the front of the RNA polymerase, which begins moving along the DNA 3) During transcription, RNA nucleotides are base-paired one after another with the template DNA bases 4) The RNA copy is released when the entire gene has been transcribed. The unwound DNA region of the DNA rewinds into a double helix -The 5’ untranslated region is translated well before the start codon (the start codon is not the first three bases to be transcribed) -Start codons will not exist in non protein-coding genes, where RNA will never be translated Transcription in Eukaryotes -Multiple RNA polymerases, each recognising distinct promoters -Primary transcripts are processed through an addition of a 5’ cap, a 3’ polyA tail, and the removal of introns by a spliceosome Removal of Introns -Prokaryotes terminate their transcription with the “loop”, the large complex formed by a collection of snRPS that loops out of the intron and brings the two exon ends close together -In eukaryotes, the polyA cleavage clipping site is transcribed; it is recognized and cut by an enzyme called RNAase, and then the polyA-polymerase adds the polyA tail. This is how
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This note was uploaded on 04/04/2009 for the course BIOLOGY 1222 taught by Professor Haffie during the Spring '09 term at UWO.

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Lecture 34-Gene Regulation - Lecture 34- Gene Regulation...

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