Lecture 13 SLIDES

Lecture 13 SLIDES - ANNOUNCEMENTS Wednesday, March 3rd...

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ANNOUNCEMENTS – Wednesday, March 3rd Problem Set 5 now posted on website – final set! Practice Final Exam will be posted by the end of the week. Review Session for Final Exam will be held Saturday, March 13 th from 5-7PM in Center 115. Link to HHMI animations on class home page. From Genes to Proteins http://www.youtube.com/watch? v=d1UPf7lXeO8&feature=related From Genes to Proteins The Flow of Genetic Information The information content of DNA is in the form of specific sequences of nucleotides along the strands. DNA information dictates protein synthesis , called gene expression , in two major stages: 1. transcription 2. translation
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Genes Specify Proteins: Evidence from Metabolic Defects Archibald Garrod (1909) Suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions Beadle and Tatum Used X-rays to mutate bread mold, creating genetic mutants that could not survive on minimal medium Mutants in Different Genes Required for Arginine Biosynthesis Three classes of mutants that could grow only with the addition of three different arginine intermediates Figure 17.2 Class I Mutants Class II Mutants Class III Mutants Wild type Minimal medium (MM) (control) MM + Ornithine MM + Citrulline MM + Arginine (control) Growth! Growth! Growth! Growth! No Growth No Growth No Growth Growth! Growth! Growth! No Growth No Growth No Growth Growth! No Growth Growth! Growth! Different Genes Responsible for Production of Specific Enzymes Class I Mutants (mutation in gene A ) Class II Mutants (mutation in gene B ) Class III Mutants (mutation in gene C ) Wild type Gene A Gene B Gene C Precursor Precursor Precursor Precursor Ornithine Ornithine Ornithine Ornithine Citrulline Citrulline Citrulline Citrulline Arginine Arginine Arginine Arginine Enzyme A Enzyme B Enzyme C A A A B B B C C C Mutants only grew if provided with the intermediates normally formed after step (mutated) enzyme functions “One Gene -> One Enzyme” Beadle and Tatum Hypothesis that the function of a gene is to dictate the production of a specific enzyme (or protein, polypeptide, RNA…)
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Two Steps of Gene Expression 1. RNA Transcription – the synthesis of RNA under the direction of DNA – Produces messenger RNA (mRNA) – Occurs in the nucleus (…RNA Processing…) 2. Protein Translation – synthesis of a polypeptide under direction of mRNA – Occurs on ribosomes Prokaryotes Eukaryotes Figure 17.3a TRANSLATION TRANSCRIPTION DNA mRNA Ribosome Polypeptide The Central Dogma: DNA RNA Protein Without nucleus, simultaneous transcription and translation TRANSCRIPTION RNA PROCESSING TRANSLATION mRNA DNA Pre-mRNA Polypeptide Ribosome Nuclear envelope With nucleus, transcription and translation separated and requires RNA processing The Genetic Code How do nucleic acids correspond to an amino acid? Codons
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This note was uploaded on 04/03/2010 for the course BIOLOGY BILD 1 taught by Professor Traver during the Winter '10 term at UCSD.

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Lecture 13 SLIDES - ANNOUNCEMENTS Wednesday, March 3rd...

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