Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 17 From Gene to Protein

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Basic Principles of Transcription and Translation Transcription = DNA  mRNA (mRNA = messenger RNA) Translation = mRNA  polypeptide – Occurs on ribosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Basic Principles of Transcription and Translation Transcription = DNA  mRNA (mRNA = messenger RNA) Translation = mRNA  polypeptide – Occurs on ribosomes DNA  mRNA  polypeptide

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes – Transcription and translation occur together Figure 17.3a

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotes - Transcription occurs in nucleus

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotes - RNA transcripts are modified before becoming true mRNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotes - Translation occurs in cytoplasm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular chain of command – DNA  RNA  amino acid (protein)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Codons: Triplets of Bases

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Codons: Triplets of Bases Codon

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Codons: Triplets of Bases

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cracking the Code Codon = 1. Translated into an amino acid 2. Serves as a translational start/stop signal

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DNA sequences in gene: 1.CCTCAGAGTGTG 2.TACGTTGCGCCC TRANSCRIPTION RNA sequence = ? TRANSLATION Amino acid sequence = ?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Codons must be read in the correct reading frame Ex: “The red dog ate the cat” – Change reading frame “her edd oga tet hec at”

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 17.2: Transcription DNA  RNA: a closer look

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RNA synthesis Catalyzed by RNA polymerase 1. Pries the DNA strands apart 2. Adds and Hooks together the RNA nucleotides

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Synthesis of an RNA Transcript 3 stages of transcription: 1. Initiation 2. Elongation 3. Termination

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 1. Initiation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Initiation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Elongation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3. Termination

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Synthesis of an RNA Transcript

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transcription Elongation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3 steps of transcription 1. Initiation –more specific in Eukaryotes 2. Elongation 3. Termination

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Initiation of Transcription Prokaryote Vs. Eukaryote Promoters: Prok. = RNA Pol Bind to promoter sequence Euk. = Transcription factors bind first to TATA box  then RNA pol II binds

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Concept 17.4 Translation = RNA directed synthesis of a polypeptide mRNA  polypeptide

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Translation Takes place in the cytoplasm Ribosome attaches to an mRNA Codon mRNA message  polypeptide by tRNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings tRNA- transfer RNA: 1. specific amino acid attachment site 2. base triplet called an anticodon on one end ANTI-CODON Amino acid attachment site

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings tRNA- transfer RNA: 1. specific amino acid attachment site 2. base triplet called an anticodon on one end Anti-Codon? Amino acid? GGA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings tRNA- transfer RNA: 1. specific amino acid attachment site 2. base triplet called an anticodon on one end CCU Glycine GGA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes have 2 subunits (small + large) Hold the tRNA and mRNA close together during translation Large Subunit Small Subunit tRNA binding sites mRNA binding site AP EPA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Building a Polypeptide We can divide translation into three stages – Initiation – Elongation – Termination

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Initiation mRNA, tRNA, and ribosome subunits assemble

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elongation: step 1- codon recognition

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elongation: Step 2- peptide bond formation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elongation:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elongation: Step 3- translocation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Termination of Translation: Step 3 Ribosome reaches a stop codon in the mRNA Release Factor

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 17.7 Mutations- changes in the genetic material of a cell – Point mutations changes in just one base pair of a gene

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Normal Figure 17.23

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Normal Point Mutation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of Point Mutations Point mutations – Base-pair substitutions – Base-pair insertions or deletions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Substitutions A base-pair substitution – Can cause missense or nonsense Figure 17.24

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Missense

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nonsense

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Insertions and Deletions Insertions and deletions – Are additions or losses of nucleotide pairs in a gene – May produce frameshift mutations Figure 17.25

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Review Transcription: DNA  mRNA Promoter, TATA box, Transcription factors, RNA Polymerase Translation: mRNA  polypeptide Small and Large ribosome subunits, mRNA, tRNA, amino acids, EPA sites

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review Ch 17: Transcription and Translation Transcription: 3 stages Initiation, elongation, termination mRNA processing Translation : 3 stages Initiation, elongation, termination DNA mutations