LECTURE 14 BILD1 S10

LECTURE 14 BILD1 S10 - Announcements Holiday Schedule...

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1 Announcements Holiday Schedule Monday, May 31st! No class, sections or office hours. Please see website for make-up Section times. Office Hours, TA Arek this Friday, May 21 , 10-11 AM, PC Foyer Office Hours, TA Thao Wednesday, June 2 , 12-1 PM, Café Roma Section A01, TA Patricia TBD Section A02, TA Arek Friday, May 28 , 10-11 AM, PC Foyer Lecture 14 From Genes to Proteins: 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 dictates protein synthesis ( gene expression ) in two major stages: 1. Transcription 2. Translation 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…
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2 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! No 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 the step when (mutated) enzyme functions “One Gene One Enzyme” Beadle and Tatum Hypothesized that the function of a gene is to dictate the production of a specific enzyme.* *or protein, polypeptide, RNA… 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 (1.5 RNA Processing…) 2. Protein Translation – synthesis of a polypeptide under direction of mRNA – Occurs on ribosomes
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3 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 transcription translation The Genetic Code How do nucleic acids correspond to an amino acid ? Codons
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This note was uploaded on 10/16/2010 for the course BILD 1 taught by Professor Boulanger during the Spring '08 term at UCSD.

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LECTURE 14 BILD1 S10 - Announcements Holiday Schedule...

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