Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter 15 Translation and Proteins Lectures by David Kass with contributions from John C. Osterman. Copyright © 2009 Pearson Education, Inc.
Central Dogma
Copyright © 2009 Pearson Education, Inc. Ribosomes consist of ribosomal proteins and ribosomal RNAs (rRNAs). have a large subunit and a small subunit. The rRNAs provide for important catalytic functions associated with translation. Section function.jpg
Copyright © 2009 Pearson Education, Inc. Figure 15.1
Copyright © 2009 Pearson Education, Inc. tRNAs 75–90 nucleotides long and contain posttranscriptionally modified bases. 2-dimensional structure of tRNAs is a cloverleaf. Section 15.1
Copyright © 2009 Pearson Education, Inc. Modified Bases (unusual bases)
Copyright © 2009 Pearson Education, Inc. Figure 15.3
Copyright © 2009 Pearson Education, Inc. Aminoacyl tRNA synthetase charges (activates) tRNAs with the appropriate amino acid. Section 15.1
Copyright © 2009 Pearson Education, Inc. 15.2Translation of mRNA Can Be Divided into Three Steps Initiation Elongation Termination
Copyright © 2009 Pearson Education, Inc. Initiation requires: the small and large ribosomal subunits mRNA GTP charged initiator tRNA initiation factors Section 15.2
Copyright © 2009 Pearson Education, Inc. Figure 15.6
Copyright © 2009 Pearson Education, Inc. Elongation requires both ribosomal subunits assembled with the mRNA to form the P (peptidyl) site and A (aminoacyl) site.
Copyright © 2009 Pearson Education, Inc. Termination is signaled by a stop codon (UAG, UAA, UGA) in the A site. Section 15.2
Copyright © 2009 Pearson Education, Inc. Polysomes (or polyribosomes) are mRNAs with several ribosomes translating at once. Section 15.2
Copyright © 2009 Pearson Education, Inc. In eukaryotes: the ribosomes are larger than in bacteria transcription and translation are spatially and temporally separated Translation Is More Complex in Eukaryotes
Copyright © 2009 Pearson Education, Inc. Variation in Protein Structure Provides the Basis of Biological Diversity Following translation, polypeptides fold up and assume higher order structures, and they may interact with other polypeptides. Section 15.9
Copyright © 2009 Pearson Education, Inc. Amino acids all have: a carboxyl group an amino group an R (radical) group bound a central carbon atom The R group of an amino acid confers specific chemical properties. Section 15.9
Copyright © 2009 Pearson Education, Inc. Amino Acid Structure
Copyright © 2009 Pearson Education, Inc. Figure 15.16
Copyright © 2009 Pearson Education, Inc. Peptide bond forms by a dehydration reaction between the carboxyl group of one amino acid and the amino group of another. Section 15.9
Copyright © 2009 Pearson Education, Inc. There are 4 levels of protein structure: Primary Sequence of amino acids Secondary Tertiary Quaternary Section 15.9
Copyright © 2009 Pearson Education, Inc. Figure Secondary Structure
Copyright © 2009 Pearson Education, Inc. Figure Tertiary Structure
Copyright © 2009 Pearson Education, Inc. Figure Quaternary Structure
Copyright © 2009 Pearson Education, Inc. Some proteins may be posttranslationally modified. These modifications are crucial to the functional capability of the final protein product. Section 15.10
Copyright © 2009 Pearson Education, Inc Proteins Function in Many Diverse Roles
Copyright © 2009 Pearson Education, Inc. Protein molecules may have domains that fold independently of the rest of the protein into stable, unique conformations. Different protein domains impart different functional capabilities. Section 15.12