Chapter 13_post

Genetics: A Conceptual Approach

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Unformatted text preview: Chapter 13 Transcription Dr. Ed Otto George Mason University Key objectives Examine the major classes of RNA present in prokaryotic and eukaryotic cells Understand the process of transcription in bacteria Understand how this process differs in eukaryotes Central Dogma Three major pathways of information flow within the cell: 1. Replication: information passes from one DNA molecule to other DNA molecules 2. Transcription: information passes from DNA to RNA 3. Translation: information passes from RNA to protein Ch.12 Ch.15 RNA Review: Structure of RNA RNA is a polymer of ribonucleotides - ribonucleotides contain ribose sugar, which has a 2’-OH group RNA contains uracil instead of thymine (e.g. more rapidly degraded under alkaline conditions) Although RNA is single-stranded, short complementary regions within the strand can pair and form secondary structures (hairpins, stem-loop structures)- In RNA, which lacks thymine, uracil pairs with adenine Because secondary structures of RNA are determined by their base sequence, different RNA molecules can assume different secondary structures Because function follows structure, RNA molecules have the potential for tremendous variation in function Review: Structure of RNA DNA vs RNA Classes of RNA Three major classes of RNA present in prokaryotic and eukaryotic cells 1.Ribosomal RNAs (rRNA) 1.Messenger RNAs (mRNA) 1.Transfer RNAs (tRNA) Combine with ribosomal protein subunits to form ribosomes, the site of protein assembly Carry the coding instructions for proteins from DNA to the ribosome; provide templates for the joining of amino acids Serve as a link between the coding sequence in the mRNA and the amino acid sequence in the polypeptide chain. Each tRNA is attached to one particular amino acid Classes of RNA Additional classes of RNA present only in eukaryotic cells 1.Pre-messenger RNAs (pre- mRNA) 1.Small nuclear RNAs (snRNA) 1.Small nucleolar RNAs (snoRNAs) mRNA precursors that are modified extensively before becoming mRNA Combine with small protein subunits to form small nuclear ribonucleoproteins (snRNPs or “snurps”); involved in converting pre-mRNA into mRNA (Ch. 14) Take part in the processing of rRNAs (Ch. 14) Classes of RNA Additional classes of RNA present only in eukaryotic cells 1.microRNAs (miRNAs) & small interfering RNAs (siRNAs) Small and abundant RNAs that take part in RNA interference (RNAi), a process in which these RNAs help trigger the degradation of mRNAs or inhibit their translation into protein (Ch. 14) Transcription All cellular RNAs are synthesized from DNA templates through the process called ______________- Exception: some viral RNAs are copied from RNA Transcription is similar to replication, but a fundamental difference is the length of the template used:- Replication– all of the nucleotides in the DNA template are copied- Transcription– only small parts of the DNA molecule, usually a single gene, or at most a few genes, are transcribed into RNA Transcription...
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This note was uploaded on 05/06/2010 for the course BIO 311 taught by Professor Otto during the Spring '10 term at George Mason.

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Chapter 13_post - Chapter 13 Transcription Dr. Ed Otto...

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