1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 10 Molecular Biology of the Gene

2. FROM DNA TO PROTEIN - Part 2: Translation © 2012 Pearson Education, Inc.

3. Genes Determine the Production of RNA and Proteins  Gene = a DNA sequence that specifies an RNA or protein sequence  Transcription is the synthesis of RNA under the direction of DNA.  DNA mRNA (recipe for protein’s amino acid seq)  DNA tRNA  DNA rRNA  Translation is the synthesis of proteins under the direction of RNA. © 2012 Pearson Education, Inc. Used in translation of mRNA

4. Figure 10.7 DNA molecule Gene 1 Gene 2 Gene 3 A Transcription RNA TranslationCodon Polypeptide Amino acid AAC C GG C AAAA UU GGCCG UUUU DNA U

5. 10.15 Review: The flow of genetic information in the cell is DNA  RNA  protein  Transcription is the synthesis of RNA from a DNA template. In eukaryotic cells, –transcription occurs in the nucleus and –the mRNA must travel from the nucleus to the cytoplasm. © 2012 Pearson Education, Inc.

6. 10.15 Review: The flow of genetic information in the cell is DNA  RNA  protein  Translation can be divided into four steps, all of which occur in the cytoplasm: 1.amino acid attachment, 2.initiation of polypeptide synthesis, 3.elongation, and 4.termination. © 2012 Pearson Education, Inc.

7. Figure 10.8A Second base Third base First base

8. Transfer RNA (tRNA) match appropriate amino acid with codon in mRNA Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon A simplified schematic of a tRNA A tRNA molecule, showing its polynucleotide strand and hydrogen bonding Anticodon is group of 3 nucleotides complementary to codon in mRNA DNA: 3’-TAC-5’ mRNA: 5’-AUG-3’ tRNA: 3’-UAC-5’

9. Figure 10.11B Enzyme tRNA ATP Protein synthesis takes a lot of ATP!

10. Figure 10.15_2 Translation Amino acid Enzyme CYTOPLASM Amino acid attachment 2 tRNA ATP Anticodon Initiation of polypeptide synthesis Large ribosomal subunit Initiator tRNA Start Codon Small ribosomal subunit mRNA 23

11. Ribosomes build proteins  Translation occurs on the surface of the ribosome. –Ribosomes bring together mRNA and tRNA and catalyze attachment of each amino acid in protein. © 2012 Pearson Education, Inc. tRNA binding sites mRNA binding site Large subunit Small subunit P site A site  Ribosomes have two subunits: small and large. –Each subunit is composed of rRNA and proteins.

12. Details of Translation  Initiation –Small subunit of ribosome binds mRNA –tRNA-Met binds to first AUG codon –Large subunit sits down - placing tRNA-Met at P site © 2012 Pearson Education, Inc. Initiator tRNA mRNA Start codon Small ribosomal subunit Large ribosomal subunit P site A site Met AUG U A C 2 AUG U A C 1 Animation: Translation

13. Figure 10.13A Start of genetic message Cap End Tail Remember - AUG marks start of protein Stop codon marks end!

14. Polypeptide mRNA Codon recognition Anticodon Amino acid Codons P site A site 1 Codon recognition: The anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome Elongation

15. Polypeptide mRNA Codon recognition Anticodon Amino acid Codons P site A site 1 Peptide bond 2 formation Elongation Peptide bond formation: The new amino acid is joined to the chain.

16. Polypeptide mRNA Codon recognition Anticodon Amino acid Codons P site A site 1 Peptide bond 2 formation Translocation 3 New peptide bond Elongation Translocation: tRNA is released from the P site and the ribosome moves tRNA from the A site into the P site

17. Polypeptide mRNA Codon recognition Anticodon Amino acid Codons P site A site 1 Peptide bond 2 formation Translocation 3 New peptide bond Stop codon mRNA movement Elongation Translocation: tRNA is released from the P site and the ribosome moves tRNA from the A site into the P site

18.  Ribosome reaches a stop codon, –the completed protein is freed from the last tRNA, and –the ribosome splits back into its separate subunits. Termination © 2012 Pearson Education, Inc.

19. Figure 10.15_3 4 Elongation Growing polypeptide New peptide bond forming Codons mRNA Polypeptide Termination Stop codon 5

20. Mutations can change the meaning of genes  A mutation is any change in the nucleotide sequence of DNA.  Single nucleotide substitution  One nucleotide changed for another  Silent - no effect in protein sequence  Missense - amino acid change  Nonsense - stop codon introduced © 2012 Pearson Education, Inc. Normal hemoglobin DNAMutant hemoglobin DNA mRNA Sickle-cell hemoglobin Normal hemoglobin Glu Val C T T G A A CT GA A U

21. Mutations can change the meaning of genes © 2012 Pearson Education, Inc.  Nucleotide Addition or Deletion (Frameshift)  Alters reading frame  Sequence of every amino acid altered after mutation.

22. Figure 10.16B Normal gene Nucleotide substitution Nucleotide deletion Nucleotide insertion Inserted Deleted mRNA Protein Met Lys Phe Lys Phe Ala Gly Ser AUGAAGUUU GGC G CA GC G CA A G UUU AUGAA Met Lys Ala His Leu GUU AUGAA GGC G CA U U Met Lys Ala His Leu GUU AUGAA G G C UG G C