Chapter 17 From Gene to Protein

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Chapter 17From Gene to Protein
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Question?

• How does DNA control a cell?

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For tests

• Name(s) of experimenters
• Outline of the experiment
• Result of the experiment and its importance

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1909 - Archibald Garrod
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Example
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George Beadle and Edward Tatum
Neurospora Pink bread mold
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Experiment
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Results
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Conclusion
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Current Hypothesis
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Central Dogma

• DNA
• Transcription
• RNA
• Translation
• Polypeptide

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Explanation
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Genetic Code
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Code Basis

• If you use

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If you use
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If you use
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Genetic Code
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Codon
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Codon Dictionary
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For Testing
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Code Redundancy
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Reading Frame
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Code Evolution
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Transcription
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Transcription Steps
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RNA Polymerase
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RNA Polymerase Binding
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RNA Polymerase Binding Needs
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Promoters
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TATA Box
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Transcription Factors
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Transcription Initiation Complex
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Initiation
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Comment

• Getting Transcription started is complicated.
• Gives many ways to control which genes are
  decoded and which proteins are synthesized.

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Elongation
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Elongation
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Comment
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Termination
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Final Product
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Modifications of RNA
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5' Cap
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Poly-A Tail
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Comment
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RNA Splicing
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Introns
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Exons
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Spliceosome
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snRNA
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snRNPs
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Result
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Ribozymes
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Introns - Function
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Final RNA Transcript
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Alternative Splicing
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Another Example
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• Bcl-XL inhibits apoptosis
• Bcl-XS induces apoptosis
• Two different and opposite effects!!

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DSCAM Gene
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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.

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Translation
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Materials Required
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Transfer RNA tRNA
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Structure of tRNA
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Anticodon
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Example
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Comment
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Importance
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Aminoacyl-tRNA Synthetases
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Ribosomes
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Large subunit
Proteins
rRNA
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Both sununits
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Large Subunit
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Translation Steps
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Initiation
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Initiation Steps
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Initiation
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Elongation Steps
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Codon Recognition
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Peptide Bond Formation
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After bond formation
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Translocation
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Comment

• Elongation takes 60 milliseconds for each AA
  added.

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Termination
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Polyribosomes
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Prokaryotes
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Comment

• Polypeptide usually needs to be modified before
  it becomes functional.

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Examples
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Signal Hypothesis
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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).

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Mutations
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Mutation types - Cells
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Point or Spot Mutations
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Types of Point Mutations
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Base-Pair Substitution
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Sickle Cell Anemia
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Types of Substitutions
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Question?

• What will the "Wobble" Effect have on Missense?

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Missense Effect
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Nonsense Effect
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Sense Mutations
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Insertions Deletions
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Frame Shift
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Question?

• Loss of 3 nucleotides is often not a problem.
• Why?

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Mutagenesis
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Spontaneous Mutations
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Mutagens
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Comment

• Any material that can chemically bond to DNA,
  or is chemically similar to the nitrogen bases,
  will often be a very strong mutagen.

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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.

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Summary

• Be able to discuss RNA and protein processing.
• Be able to describe and discuss DNA mutations.

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Commentary

• Beadle and Tatums work is currently being upset.
• One gene may give many polypeptides through a
  process called Alternate Splicing.