From DNA to RNA - Protein Synthesis: How Cells Read the...

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Protein Synthesis: How Cells Read the Genome: From DNA to Protein From DNA to RNA: Transcription and translation are the means by which cells read out or express the genetic information in their genes. The gene sequences of DNA are transcribed by RNA polymerase enzymes into the form of single stranded mRNA molecules. These are translated by ribosomes into protein. Protein Biosynthesis: some challenging issues: The -COOH in an amino acid is not reactive enough to give a condensation reaction with NH2 of another amino acid. Diverse polypeptides must be made based on genetic instructions encoded in mRNAs The chain must be elongated by one a -amino acid unit at a time. The error rate must be kept low The production site(s) must be suitable for production and product delivery Protein production must be efficient and regulated Cells produce several types of RNA: Messenger RNA (mRNA): RNA molecules copied from genes in DNA that specify amino acid sequence of a protein. Code for proteins. Ribosomal RNA (rRNA) : form basic structure of ribosome; catalyze protein synthesis. Transfer RNA (tRNA): central to protein synthesis as adaptors b/w mRNA and amino acids Small nuclear RNA (snRNA): function in a variety of nuclear processes, including splicing of pre-mRNA Small nucleolar RNA ( snoRNA): used to process and chemically modify rRNA Small cajal RNA (scaRNA): used to modify snoRNA and snRNA microRNA (miRNA): regulate gene expression by blocking translation of selective mRNAs small interfering RNA (siRNA) : turn off gene expression by directing degradation of selective mRNAs and the establishment of compact chromatin structures. Why RNA polymerase II also requires activator, mediator, and chromatin modifying proteins: DNA in eucaryotes is packaged into nucleosomes which are further arranged in higher- order chromatin structures. Gene regulatory proteins called transcriptional activators must bind specific sequences in DNA and help attract RNA polymerase II to start point of transcription. Activators are one of main ways that cells regulate gene expression. Second, eukaryotic transcription initiation requires prescence of a protein complex called Mediator, which allows activator proteins to communicate properly with polymerase II and w/ GTFs Finally, transcription initiation requires local recruitment of chromatin-modifying enzymes including chromatin remodeling complexes and histone-modifying enzymes, both of which allow greater access to DNA present in chromatin
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The Process of Transcription: General Steps: I. DNA Transcription/m-RNA Synthesis: A. Transcription: the synthesis of RNA under the direction of DNA 1. When the cell needs a particular protein, the nucleotide sequence of the appropriate portion of the DNA molecule in a chromosome must first be
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This note was uploaded on 03/20/2008 for the course CBIO 3400 taught by Professor Shen,kipreos during the Spring '08 term at University of Georgia Athens.

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From DNA to RNA - Protein Synthesis: How Cells Read the...

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