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Chapter 17: From Gene to Protein

Chapter 17: From Gene to Protein. Objectives 1. To understand the central dogma To understand the process of transcription To understand the purpose and structure of RNA To understand the process of translation To understand the types of mutations that can occur.

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Chapter 17: From Gene to Protein

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  1. Chapter 17: From Gene to Protein Objectives 1. To understand the central dogma To understand the process of transcription To understand the purpose and structure of RNA To understand the process of translation To understand the types of mutations that can occur

  2. The Central Dogma is based on the triplet code

  3. Three basic stages of transcription 1. Initiation (No primer needed) 2. Elongation (5’ to 3’) 3. Termination Important vocabulary 1. “Upstream” 2. “Downstream” 3. RNA Polymerase 4. Template Strand 5. Promotor 6. Terminator 7. Transcription Unit

  4. Difference between Prokaryotic and Eukaryotic Cells Use of transcription help RNA Poly II attach Eukaryotic cells use more then one type of Polymerase use of a transcriptioncomplex Use of a TATA box

  5. Eukaryotic Pre-mRNA needs to be modified before leaving nucleus in two main stages Alteration of the ends -Aid in Export of mRNA -Help protect from enzymes -Help in attachment to Ribosomes Gene splicing -Cut out Introns (Noncoding RNA) -Splice Exons (RNA that is expressed) -Use of spliceosomes ”Cut and Paste” *Consist of small nucear ribonucleicproteins **Recognize sequences in introns Evolutionary significance RNA has catalytic role (snRNA) in Eukaryotic Cells and in protozoan (p. 336) Why can RNA act as an enzyme (Ribozyme)? Alternative RNA splicing --- One exon codes for one domain of a protein (p. 336) Introns allow for more crossing over without disrupting domain coding = new proteins sequences.

  6. Translation Overview -mRNA brings code (codon or triplet) to ribosomes -tRNA with anticodon brings a specific amino acid to ribosomes -Polypeptide bonds are made between amino acids

  7. Structure and Function on tRNA -tRNA is transcribed in the nucleus -tRNA contains an anti-codon that is anti-parallel to the codons -Uses an enzyme aminoacyl-tRNA synthetase to bond a specific amino acid to the 3’ end Two processes responsible accurate translation tRNA specically carries one amino acid The anti-codon matches mRNA in the ribosomes (Wobble exists in the third base of the triplet which allows for some flexibility)

  8. Ribosomal Structure

  9. Building a Polypeptide • Initiation -start codon -Large ribosomal sub-unit -rRNA is thought be be responsible for structure • Elongation - A site -- P site -- E site -anti-codon recognizes codon -Peptide bond formed between P and A site -tRNA is translocated from A to P site and the empty tRNA exits the ribosome • Termination -Release factor bonds to the stop codon

  10. Base-pair substitutions Missense - change one amino acid to another. Nonsense - Changes codon to stop codon terminating translation. Insertions and Deletions Result in frameshift mutations

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