BIOLOGY. Chapter 15 Genes & Proteins

BIOLOGY Chapter 15 Genes & Proteins

CMPBELL BIOLOGY TENTH EDITION Reece Urry Cain Wasserman Minorsky Jackson 17 Protein Synthesis 2014 Pearson Education, Inc.

Fig. 17-1

Figure 17.1a n albino racoon

Condition Fig. 17-2 EXPERIMENT Growth: Wild-type cells growing and dividing Minimal medium No growth: Mutant cells cannot grow and divide Tatum & Beadle, 1941 1 gene = 1 enzyme 1 gene = 1 polypeptide RESULTS Minimal medium (MM) (control) Classes of Neurospora crassa Wild type Class I mutants Class II mutants Class III mutants MM + ornithine MM + citrulline MM + arginine (control) CONCLUSION Wild type Class I mutants (mutation in gene ) Class II mutants (mutation in gene B) Class III mutants (mutation in gene C) Gene Gene B Gene C Precursor Precursor Precursor Precursor Enzyme Enzyme Enzyme Enzyme Ornithine Ornithine Ornithine Ornithine Enzyme B Enzyme B Enzyme B Enzyme B Citrulline Citrulline Citrulline Citrulline Enzyme C Enzyme C Enzyme C Enzyme C rginine rginine rginine rginine

Protein Synthesis Overview Eukaryotic cells Transcription DN RN RN Processing Modify pre-mrn Translation RN proteins

Fig. 17-4 DN molecule Gene 1 Gene 2 Gene 3 DN template strand TRNSCRIPTION mrn Codon TRNSLTION Protein mino acid

Translation Builds the Protein DN DN template strand TRNSCRIPTION T T C G T C G G U C G U C mrn Codon Codon Codon TRNSLTION Lysine Serine Valine Protein Polypeptide (amino acid sequence) codon is a three-nucleotide sequence that encodes one amino acid. Section 7.5 Figure 7.12

Eukaryotic Protein Synthesis Overview Figure 15.3 Transcription DN pre- mrn RN Processing Pre-mRN mrn Translation mrn protein

First mrn base ( end of codon) Third mrn base ( end of codon) Fig. 15.4 Second mrn base

TRNSCRIPTION Figure 17.24a Protein synthesis overview DN RN transcript RN PROCESSING CYTOPLSM Exon NUCLEUS RN polymerase RN transcript (pre-mrn) Intron mino acid trn minoacyl-trn synthetase MINO CID CTIVTION mrn minoacyl (charged) trn

Fig. 17-3b-1 Nuclear envelope TRNSCRIPTION DN Pre-mRN (b) Eukaryotic cell

Fig. 17-7 Promoter Transcription unit Transcription Overview Start point RN polymerase DN 1 Initiation Elongation Nontemplate strand of DN Unwound DN RN transcript Template strand of DN 2 Elongation RN polymerase end RN nucleotides Rewound DN RN transcript 3 Termination Completed RN transcript Newly made RN Direction of transcription ( downstream ) Template strand of DN

Fig. 17-7a-1/ 15.7 Promoter Start point RN polymerase Transcription unit DN Transcription - Inititation

Fig. 17-8/ 15.7 & 15.10 TT box Transcription factors 1 Promoter 2 eukaryotic promoter includes a TT box Start point Template Template DN strand Several transcription factors must bind to the DN before RN polymerase II can do so. RN polymerase II 3 dditional transcription factors bind to the DN along with RN polymerase II, forming the transcription initiation complex. Transcription factors RN transcript Transcription initiation complex

Figure 15.10 Promoter region with TT Box Transcription factors bind to TT Box RN polymerase II then binds and forms the transcription initiation complex with transcriptional factors

Fig. 17-7a-3 Promoter Start point RN polymerase Transcription unit DN 1 Initiation Transcription - Elongation Unwound DN RN transcript Template strand of DN 2 Elongation Rewound DN RN transcript

Fig. 17-7b Elongation Nontemplate strand of DN RN polymerase RN nucleotides end Newly made RN Direction of transcription ( downstream ) Template strand of DN

Fig. 17-7a-4 Promoter Start point RN polymerase Transcription unit DN 1 Initiation Transcription -Termination Unwound DN RN transcript Template strand of DN 2 Elongation Rewound DN RN transcript 3 Termination Completed RN transcript

Fig. 17-3b-2 Nuclear envelope TRNSCRIPTION DN RN PROCESSING Pre-mRN mrn (b) Eukaryotic cell

Figure 17.11/15.11 RN Processing 5 end cap guanine cap 3 end poly- tail Introns removed Exons spliced together modified guanine nucleotide added to the end G P P P Cap UTR Region that includes protein-coding segments Start codon Stop codon Polyadenylation signal UTR 50 250 adenine nucleotides added to the end U Poly- tail

Figure 17.11/15.11 RN Processing Pre-mRN Intron Intron Cap Poly- tail 1 30 31 104 Introns cut out and exons 105 146 spliced together mrn Cap Poly- tail UTR 1 146 Coding segment UTR

Fig. 17-11-3/ 15.13 RN transcript (pre-mrn) Exon 1 Intron Exon 2 Protein snrn snrnps Other proteins Spliceosome Ribozymes T. Cech Spliceosome components mrn Exon 1 Exon 2 Cut-out intron

Fig. 18-11 lternative Splicing Exons DN Troponin T gene Primary RN transcript RN splicing mrn or

Fig. 17-12 DN Gene Exon 1 Intron Exon 2 Intron Exon 3 Transcription RN processing Translation Domain 3 Domain 2 Domain 1 Polypeptide

Fig. 17-3b-3 Nuclear envelope TRNSCRIPTION DN RN PROCESSING Pre-mRN mrn TRNSLTION Ribosome Polypeptide (b) Eukaryotic cell

Translation -mrn -trn -mino acyl trn synthetase -amino acids Polypeptide -ribosome Ribosome mino acids trn with amino acid attached Fig. 17-13 trn nticodon mrn Codons

Fig. 17-14 mino acid attachment site trn with anticodons Specific amino acid Hydrogen bonds nticodon (a) Two-dimensional structure mino acid attachment site Hydrogen bonds nticodon (b) Three-dimensional structure nticodon (c) Symbol used in this book

Fig. 17-15-4 mino acid minoacyl-trn synthetase (enzyme) P P P denosine TP P P i P denosine trn P i P i minoacyl-trn synthetase trn P denosine MP Computer model minoacyl-trn ( charged trn )

1 mino acid and trn enter active site. Tyrosine (Tyr) (amino acid) Tyrosyl-tRN synthetase Tyr-tRN U TP minoacyl-trn synthetase Complementary trn anticodon MP + 2 P i trn 3 minoacyl trn released. 2 Using TP, synthetase catalyzes covalent bonding. mino acid Computer model

Figure 17.17 trn molecules Growing polypeptide Exit tunnel E P Large subunit Small subunit mrn (a) Computer model of functioning ribosome P site (Peptidyl-tRN binding site) E site (Exit site) mrn binding site E P Exit tunnel site (minoacyltrn binding site) Large subunit Small subunit mino end mrn E Growing polypeptide Codons Next amino acid to be added to polypeptide chain trn (b) Schematic model showing binding sites (c) Schematic model with mrn and trn

Figure 17.18 U C U G P site Large ribosomal subunit Initiator trn mrn GTP P i + GDP E Start codon mrn binding site Small ribosomal subunit Translation initiation complex 1 Small ribosomal subunit binds to 2 mrn. Large ribosomal subunit completes the initiation complex.

Figure 17.19-2 mino end of polypeptide E P site site mrn GTP 1 Codon recognition GDP + P i E P 2 Peptide bond formation E P

Figure 17.19-3 Ribosome ready for next aminoacyl trn mino end of polypeptide E P site site mrn GTP 1 Codon recognition GDP + P i E E Translocation P GDP + 3 GTP P i P 2 Peptide bond formation E P

Figure 17.20-2 Translation - Termination Release factor Free polypeptide Stop codon (UG, U, or UG) 1 Ribosome reaches a 2 stop codon on mrn. Release factor promotes hydrolysis.

Fig. 17-19-3 Translation - Termination Release factor Free polypeptide Stop codon (UG, U, or UG) 2 GTP 2 GDP

Fig. 17-20 / 15.9 Polyribosome multiple transcripts Incoming ribosomal subunits Growing polypeptides Completed polypeptide (a) Start of mrn ( end) End of mrn ( end) Ribosomes mrn (b) 0.1 µm

Fig. 17-24 RN polymerase DN mrn Polyribosome RN polymerase Direction of transcription 0.25 µm DN Polyribosome Polypeptide (amino end) Ribosome mrn ( end)

Figure 17.21 Secretory proteins signal peptide 1 2 3 4 5 6 Polypeptide synthesis begins. Ribosome SRP binds to signal peptide. mrn SRP binds to receptor protein. SRP detaches and polypeptide synthesis resumes. Signalcleaving enzyme cuts off signal peptide. Completed polypeptide folds into final conformation. SRP Signal peptide Signal peptide removed ER membrane Protein CYTOSOL ER LUMEN SRP receptor protein Translocation complex

Mutations Change DN mutation is a change in a cell s DN sequence. Mutations come in several varieties. Section 7.7 Wild fly: ndrew Syred/Science Source; Mutant fly: Science VU/Dr. F. R. Turner/Visuals Unlimited Figure 7.20

Mutations Change DN Wildtype = original nucleotide sequence Substitution = changed nucleotide(s) In Bio 20 lab 1 base change Salt instead of sugar Silent mutation? Section 7.7 Table 7.2

Mutations Change DN Frameshift mutations affect multiple codons. Insertion of one nucleotide changes every codon after the insertion. Section 7.7 Table 7.2

Fig. 17-23a Wild type DN template strand mrn Protein mino end Stop Carboxyl end instead of G U instead of C Stop Subsitutition mutation = Silent (no effect on amino acid sequence) Base #3 redundancy in genetic code

Fig. 17-23b Wild type DN template strand mrn Protein mino end Stop Carboxyl end T instead of C instead of G Nucleotide-pair substitution: Missense base #1 or #2 Stop

Figure 17.25 Substitution mutation - missense Wild-type β-globin Sickle-cell β-globin Wild-type β-globin DN C T C G G Mutant β-globin DN C G T C G mrn mrn G G U G G Normal hemoglobin Glu Sickle-cell hemoglobin Val

Figure 17.26c Wild type DN template strand T T T mrn Protein mino end C C C C G T T T G G T T T G G C T U G G U U U G G C U Met Lys Phe Gly Stop Carboxyl end Nucleotide-pair substitution: nonsense instead of T T C T C C C G T T T G T G T T T G G C T U instead of U G U G U U U G G U U Met Stop

Fig. 17-23c Wild type DN template strand mrn Protein mino end Nucleotide-pair substitution: nonsense Stop Carboxyl end Nonsense instead of T U instead of Stop

Figure 17.26d Wild type DN template strand T T T mrn Protein mino end C C C C G T T T G G T T T G G C T U G G U U U G G Met Lys Phe Gly C U Stop Carboxyl end Nucleotide-pair insertion: frameshift causing immediate nonsense T Extra C T T C C C G T T T G T G T T T G G C T U G U G U U U G G C U Met Stop

Figure 17.26e Wild type DN template strand T T T mrn Protein mino end C C C C G T T T G G T T T G G C T U G G U U U G G C U Met Lys Phe Gly Stop Carboxyl end Nucleotide-pair deletion: frameshift causing extensive missense missing T C T T C C C G T T T G G T T G G C T U G G U U G G C U Met Lys Leu la U missing

Figure 17.26f Wild type DN template strand T C T T C C C G T T T G G T T T G G C T mrn Protein mino end U G G U U U G G Met Lys Phe Gly C U Stop Carboxyl end 3 nucleotide-pair deletion: no frameshift, but one amino acid missing T T C missing T C C C G T T T G T T T G G C T G missing U G U U U G G C U Met Phe Gly Stop

Figure 17.26 DN template strand mrn Protein mino end Wild type T C T T C C C G T T T G G T T T G G C T U G G U U U G G C U Met Lys Phe Gly Stop Carboxyl end (a) Nucleotide-pair substitution instead of G T T C G T T C G T T T C G C G T T T T U instead of C U G G U U U G G U U Met Lys Phe Gly Stop Silent T T instead of C C T T C T C G T T T G G T T T G C T instead of G U G G U U U G C U Met Lys Phe Ser Stop Missense (b) Nucleotide-pair insertion or deletion Extra T G T T T G G Extra U U G U G U U U Met Stop Frameshift (1 nucleotide-pair insertion) T C T T C C C G T T G T C T missing missing U G G U U G G C U Met Lys Leu la Frameshift (1 nucleotide-pair deletion) U G G C U T C T T C C C G T T T G G T T G G C T instead of T missing T C T C C C G T T T C C C T G T G T T T G G C T G G G U instead of G missing U G U G U U U G G U U G G G Met Stop Met Phe Gly Nonsense 3 nucleotide-pair deletion T T C G T T T T C T U U U U C U T Stop T

Fig. 17-25 TRNSCRIPTION DN RN transcript RN PROCESSING Exon RN polymerase RN transcript (pre-mrn) Intron NUCLEUS minoacyl-trn synthetase CYTOPLSM mino acid trn MINO CID CTIVTION E P Ribosomal subunits mrn Growing polypeptide ctivated amino acid TRNSLTION E nticodon Codon Ribosome

Fig. 17-UN4 Protein synthesis knowledge

Fig. 17-UN5 Protein synthesis transcription practice

Fig. 17-UN6 Protein synthesis translation practice Functional protein???

Fig. 17-UN7 Protein synthesis transcription & translation understanding

Fig. 17-UN8