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Figure 14.1 Figure 14.1 How does a single faulty gene result in the dramatic appearance of an albino deer? 1
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DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide
Figure 14.4a-2 DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide Figure 14.4a-2 Overview: the roles of transcription and translation in the flow of genetic information (part 1, step 2) (a) Bacterial cell 3
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Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA
Figure 14.4b-3 Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA Figure 14.4b-3 Overview: the roles of transcription and translation in the flow of genetic information (part 2, step 3) TRANSLATION Ribosome Polypeptide (b) Eukaryotic cell 4
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DNA template strand 3 5 A C C A A A C C G A G T T G G T T T G G C T
Figure 14.5 DNA template strand 3 5 A C C A A A C C G A G T T G G T T T G G C T C A 5 3 TRANSCRIPTION U G G U U U G G C U C A mRNA 5 3 Codon Figure 14.5 The triplet code TRANSLATION Protein Trp Phe Gly Ser Amino acid 5
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First mRNA base (5 end of codon) Third mRNA base (3 end of codon)
Figure 14.6 Second mRNA base U C A G UUU UCU UAU UGU U Phe Tyr Cys UUC UCC UAC UGC C U Ser UUA UCA UAA Stop UGA Stop A Leu UUG UCG UAG Stop UGG Trp G CUU CCU CAU CGU U His CUC CCC CAC CGC C C Leu Pro Arg CUA CCA CAA CGA A Gln CUG CCG CAG CGG G First mRNA base (5 end of codon) Third mRNA base (3 end of codon) AUU ACU AAU AGU U Asn Ser AUC IIe ACC AAC AGC C A Thr Figure 14.6 The codon table for mRNA AUA ACA AAA AGA A Lys Arg AUG Met or start ACG AAG AGG G GUU GCU GAU GGU U Asp GUC GCC GAC GGC C G Val Ala Gly GUA GCA GAA GGA A Glu GUG GCG GAG GGG G 6
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(a) Tobacco plant expressing a firefly gene
Figure 14.7 Figure 14.7 Expression of genes from different species (a) Tobacco plant expressing a firefly gene (b) Pig expressing a jellyfish gene 7
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Completed RNA transcript
Figure Promoter Transcription unit 5 3 3 5 Start point RNA polymerase 1 Initiation 5 3 3 5 Unwound DNA RNA transcript Template strand of DNA 2 Elongation Rewound DNA 5 3 3 3 5 5 Figure The stages of transcription: initiation, elongation, and termination (step 3) Direction of transcription (“downstream”) RNA transcript 3 Termination 5 3 3 5 5 3 Completed RNA transcript 8
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Direction of transcription Template strand of DNA
Figure 14.10 Nontemplate strand of DNA RNA nucleotides RNA polymerase T C C A A A 3 T 5 U C T 3 end T G U A G A C C A U C C A C A 5 A 3 T A G G T T Figure Transcription elongation 5 Direction of transcription Template strand of DNA Newly made RNA 9
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exons spliced together
Figure 14.12 Pre-mRNA Intron Intron 5 Cap Poly-A tail 1–30 31–104 105– 146 Introns cut out and exons spliced together mRNA 5 Cap Poly-A tail 1–146 Figure RNA processing: RNA splicing 5 UTR 3 UTR Coding segment AAUAAA 10
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DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide Figure 14.UN04
Figure 14.UN04 In-text figure, translation, p. 279 Polypeptide 11
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Amino acids Polypeptide tRNA with amino acid attached Ribosome tRNA
Figure 14.14 Amino acids Polypeptide tRNA with amino acid attached Ribosome Trp Phe Gly Figure Translation: the basic concept tRNA C C C C Anticodon A G A A A U G G U U U G G C 5 Codons 3 mRNA 12
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Animation: Translation Introduction
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Amino end of polypeptide Codon recognition Ribosome ready for
Figure Amino end of polypeptide 1 Codon recognition E 3 mRNA Ribosome ready for next aminoacyl tRNA P site A site 5 GTP GDP P i E E P A P A Figure The elongation cycle of translation (step 3) GDP P i 2 Peptide bond formation 3 Translocation GTP E P A 14
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(a) Several ribosomes simultaneously translating one mRNA molecule
Figure 14.22a Growing polypeptides Completed polypeptide Incoming ribosomal subunits Polyribosome Start of mRNA (5 end) End of mRNA (3 end) Figure 14.22a Polyribosomes (part 1: art) (a) Several ribosomes simultaneously translating one mRNA molecule 15
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RNA polymerase DNA mRNA Polyribosome Direction of transcription
Figure 14.23 RNA polymerase DNA mRNA Polyribosome Direction of transcription 0.25 m RNA polymerase DNA Figure Coupled transcription and translation in bacteria Polyribosome Polypeptide (amino end) Ribosome mRNA (5 end) 16
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(a) Nucleotide-pair substitution
Figure 14.26 Wild type DNA template strand 3 T A C T T C A A A C C G A T T 5 5 A T G A A G T T T G G C T A A 3 mRNA 5 A U G A A G U U U G G C U A A 3 Protein Met Lys Phe Gly Stop (a) Nucleotide-pair substitution (b) Nucleotide-pair insertion or deletion A instead of G Extra A 3 T A C T T C A A A C C A A T T 5 3 T A C A T T C A A A C C G A T T 5 5 A T G A A G T T T G G T T A A 3 5 A T G T A A G T T T G G C T A A 3 U instead of C Extra U 5 A U G A A G U U U G G U U A A 3 5 A U G U A A G U U U G G U U A A 3 Met Lys Phe Gly Met Stop Stop Silent (no effect on amino acid sequence) Frameshift causing immediate nonsense (1 nucleotide-pair insertion) T instead of C A missing 3 T A C T T C A A A T C G A T T 5 3 T A C T T C A A C C G A T T 5 5 A T G A A G T T T A G C T A A 3 5 A T G A A G T T G G C T A A 3 A instead of G U missing 5 A U G A A G U U U A G C U A A 3 5 A U G A A G U U G G G U A A 3 Met Lys Phe Ser Stop Met Lys Leu Ala Figure Types of small-scale mutations that affect mRNA sequence Missense Frameshift causing extensive missense (1 nucleotide-pair deletion) A instead of T T T C missing 3 T A C A T C A A A C C G A T T 5 3 T A C A A A C C G A T T 5 5 A T G T A G T T T G G C T A A 3 5 A T G T T T G G C T A A 3 U instead of A A A G missing 5 A U G U A G U U U G G U U A A 3 5 A U G U U U G G C U A A 3 Met Stop Met Phe Gly Stop Nonsense No frameshift, but one amino acid missing (3 nucleotide-pair deletion) 17
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Animation: Protein Synthesis
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Regulation of Gene Expression
15 Regulation of Gene Expression
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(a) Regulation of enzyme activity (b) Regulation of enzyme production
Figure 15.2 Precursor Feedback inhibition trpE gene Enzyme 1 Regulation of gene expression trpD gene Enzyme 2 trpC gene trpB gene Enzyme 3 Figure 15.2 Regulation of a metabolic pathway trpA gene Tryptophan (a) Regulation of enzyme activity (b) Regulation of enzyme production 20
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Operon: Genes that code for similar things are grouped together with a regulatory gene that controls their transcription
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Repressible operon: Tryptophan
Figure 15.3a Repressible operon: Tryptophan Regulatory gene Genes that code for enzymes that make tryptophan trpR trpE trpD trpC trpB trpA Operator RNA polymerase mRNA 3 mRNA 5 5 E D C B A Protein Inactive repressor Figure 15.3a The trp operon in E. coli: regulated synthesis of repressible enzymes (part 1: tryptophan absent) (a) Tryptophan absent, repressor inactive, operon on 22
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(b) Tryptophan present, repressor active, operon off
Figure 15.3b What happens when tryptophan is present? Don‘t need to make tryptophan-building enzymes! DNA No RNA made mRNA Protein Active repressor Tryptophan (corepressor) Figure 15.3b The trp operon in E. coli: regulated synthesis of repressible enzymes (part 2: tryptophan present) (b) Tryptophan present, repressor active, operon off 23
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Inducible operon: Lactose
Figure 15.4b Inducible operon: Lactose lac operon IacI IacZ IacY IacA mRNA RNA polymerase 3 Protein mRNA 5 5 -Galactosidase Permease Transacetylase Figure 15.4b The lac operon in E. coli: regulated synthesis of inducible enzymes (part 2: lactose present) Inactive repressor Allolactose (inducer) (b) Lactose present, repressor inactive, operon on 24
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(a) Lactose absent, repressor active, operon off
Figure 15.4a Regulatory gene Promoter Operator DNA lacI IacZ No RNA made 3 mRNA RNA polymerase 5 Active repressor Protein Figure 15.4a The lac operon in E. coli: regulated synthesis of inducible enzymes (part 1: lactose absent) (a) Lactose absent, repressor active, operon off 25
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Distal control element Enhancer TATA box
Figure Promoter Activators Gene DNA Distal control element Enhancer TATA box General transcription factors DNA- bending protein Group of mediator proteins RNA polymerase II Figure A model for the action of enhancers and transcription activators (step 3) RNA polymerase II Transcription initiation complex RNA synthesis 26
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Albumin gene not expressed Albumin gene expressed
Figure 15.11 Enhancer Promoter Albumin gene Control elements Enhancer Promoter Crystallin gene (a) LIVER CELL NUCLEUS (b) LENS CELL NUCLEUS Available activators Available activators Albumin gene not expressed Albumin gene expressed Figure Cell type–specific transcription Crystallin gene not expressed Crystallin gene expressed 27
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