Transcript Ch 16 PPT
Chapter 17 From Gene to Protein Question? How does DNA control a cell? For tests: Name(s) of experimenters Outline of the experiment Result of the experiment and its importance 1909 - Archibald Garrod Example George Beadle and Edward Tatum Neurospora Pink bread mold Experiment Results Conclusion Current Hypothesis Central Dogma DNA Transcription RNA Translation Polypeptide Explanation Genetic Code Code Basis If you use: If you use: If you use: Genetic Code Codon Codon Dictionary For Testing: Code Redundancy Reading Frame Code Evolution Transcription Transcription Steps RNA Polymerase RNA Polymerase Binding RNA Polymerase Binding Needs: Promoters TATA Box Transcription Factors Transcription Initiation Complex Initiation Comment Getting Transcription started is complicated. Gives many ways to control which genes are decoded and which proteins are synthesized. Elongation Elongation Comment Termination Final Product Modifications of RNA 5' Cap Poly-A Tail Comment RNA Splicing Introns Exons Spliceosome Result Ribozymes Introns - Function Final RNA Transcript Alternative Splicing Another Example – inhibits apoptosis Bcl-XS – induces apoptosis Bcl-XL Two different and opposite effects!! DSCAM Gene Commentary Alternative Splicing is going to be a BIG topic in Biology. About 60% of genes are estimated to have alternative splicing sites. One gene does not equal one polypeptide. Translation Materials Required Transfer RNA = tRNA Structure of tRNA Anticodon Example Comment Importance Aminoacyl-tRNA Synthetases Ribosomes Large subunit Proteins rRNA Both sununits Large Subunit Translation Steps Initiation Initiation Steps: Initiation Elongation Steps: Codon Recognition Peptide Bond Formation After bond formation Translocation Comment Elongation takes 60 milliseconds for each AA added. Termination Polyribosomes Prokaryotes Comment Polypeptide usually needs to be modified before it becomes functional. Examples Signal Hypothesis Result Protein is made directly into the ER . Protein targeted to desired location (e.g. secreted protein). “Clue” (the first 20 AAs are removed by processing). Mutations Mutation types - Cells Point or Spot Mutations Types of Point Mutations Base-Pair Substitution Sickle Cell Anemia Types of Substitutions Question? What will the "Wobble" Effect have on Missense? Missense Effect Nonsense Effect Sense Mutations Insertions & Deletions Frame Shift Question? Loss of 3 nucleotides is often not a problem. Why? Mutagenesis Spontaneous Mutations Mutagens Comment Any material that can chemically bond to DNA, or is chemically similar to the nitrogen bases, will often be a very strong mutagen. Summary Know Beadle and Tatum. Know the central dogma. Be able to “read” the genetic code. Be able to describe the events of transcription and translation. Summary Be able to discuss RNA and protein processing. Be able to describe and discuss DNA mutations. Commentary Beadle and Tatum’s work is currently being upset. One gene may give many polypeptides through a process called Alternate Splicing.