Translation and Operons

Transcription

1 Translation and Operons

2 You Should Be Able To 1. Describe the three stages translation. including the movement of trna molecules through the ribosome. 2. Compare and contrast the roles of three different types of RNA during translation. 3. Describe the roles of signal peptides in protein synthesis. 4. Describe the regulation of gene expression, using the lac or trp operon as an example.

3 Fig. 17-3a-2 TRANSCRIPTION TRANSLATION DNA mrna Ribosome Polypeptide (a) Bacterial cell

4 Fig. 17-3b-3 Nuclear envelope TRANSCRIPTION DNA RNA PROCESSING Pre-mRNA mrna TRANSLATION Ribosome Polypeptide (b) Eukaryotic cell

5 2011 Pearson Education, Inc.

6 2011 Pearson Education, Inc.

7 Three Stages of Translation Three Stages of Translation Initiation Elongation Termination

8 Pearson Education, Inc.

9 Also, note that this constitutes 5 Untranslated Region (UTR) of the mrna J Pearson Education, Inc.

10 Pearson Education, Inc.

11 trna: Transfer RNA

12 Transfer RNA (trna)

13 Transfer RNA (trna) Single-stranded RNAs of about nucleotides On one end, they hold an amino acid On the other end, they bind to mrna

14 64 Codons 2011 Pearson Education, Inc.

15 Transfer RNA (trna) There are about 45 different trnas in eukaryotic cells The code is conservative!

16 The Wobble Hypothesis

17 trna Structure Campbell 8e, Fig

18 Aminoacyl trnasynthetase 2011 Pearson Education, Inc.

19 Charging Transfer RNA Aminoacyl trna Synthetase + Amino acid + ATP + Uncharged trna = Charged trna Campbell 8e, Fig

20 Ribosomes and Translation Three Stages of Translation Initiation Elongation Termination

21 2011 Pearson Education, Inc.

22 Elongation

23 Ribosomes and Translation Three Stages of Translation Initiation Elongation Termination

24 Termination Termination 2011 Pearson Education, Inc.

25 Signal Peptides Campbell 8e, Fig

26 Regulation of gene expression in prokaryotes.

27 Operon A series of genes sharing a promoter and a regulatory region. Regulatory Region A region that can produce proteins to inhibit or stimulate gene expression.

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29 The Operon

30 Operon A series of genes sharing a promoter and a regulatory region. Regulatory Region A region that can produce proteins to inhibit or stimulate gene expression.

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33 trp operon

34 Fig. 18-3b-2 DNA No RNA made mrna Protein Tryptophan (corepressor) Active repressor (b) Tryptophan present, repressor active, operon off

35 Fig. 18-3a trp operon DNA Promoter Regulatory gene mrna Protein 5 trpr trpe trpd trpc trpb Operator Start codon Stop codon 3 RNA mrna 5 polymerase E D C B Inactive repressor Promoter (a) Tryptophan absent, repressor inactive, operon on Genes of operon trpa Polypeptide subunits that make up the enzyme tryptophan synthase A

36 Fig trp operon DNA Promoter Regulatory gene mrna 5 Promoter Genes of operon trpr trpe trpd trpc trpb Operator Start codon Stop codon 3 RNA mrna 5 polymerase E D C B Protein Inactive Polypeptide subunits that make up repressor enzymes for tryptophan synthase (a) Tryptophan absent, repressor inactive, operon on trpa A DNA No RNA made mrna Protein Tryptophan (corepressor) Active repressor (b) Tryptophan present, repressor active, operon off

37 lac operon

38 Fig trp operon DNA Promoter Regulatory gene mrna 5 Promoter Genes of operon trpr trpe trpd trpc trpb Operator Start codon Stop codon 3 RNA mrna 5 polymerase E D C B Protein Inactive Polypeptide subunits that make up repressor enzymes for tryptophan synthase (a) Tryptophan absent, repressor inactive, operon on trpa A DNA No RNA made mrna trp operon Protein Tryptophan (corepressor) Active repressor (b) Tryptophan present, repressor active, operon off

39 You Should Be Able To 1. Describe the three stages translation. including the movement of trna molecules through the ribosome. 2. Compare and contrast the roles of three different types of RNA during translation. 3. Describe the roles of signal peptides in protein synthesis. 4. Describe the regulation of gene expression, using the lac or trp operon as an example.

40 Translation and Operons