Ch. 10 Notes DNA: Transcription and Translation

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Ch. 10 NotesDNA Transcription and Translation
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GOALS

• Compare the structure of RNA with that of DNA
• Summarize the process of transcription
• Relate the role of codons to the sequence of
  amino acids that results after translation
• Outline the major steps of translation
• Discuss the evolutionary significance of the
  genetic code
• Describe how the lac operon is turned on or off
• Summarize the role of transcription factors in
  regulating eukaryotic gene expression
• Describe how eukaryotic genes are organized
• Evaluate three ways that point mutations can
  alter genetic material

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Decoding the Information in DNA

• RNA

• 1. Nucleic acid made of nucleotides linked
  together
• 2. Single stranded

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Decoding the Information in DNA

• RNA

• 3. Contains 5C ribose sugar (one more oxygen
  than DNA)

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Decoding the Information in DNA

• RNA

• 4. Has A, G and C bases, but no T
• 5. Thymine replaced by uracils (which pairs with
  adenine)

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Decoding the Information in DNA

• Transcription

• Instructions for making protein are transferred
  from a gene to an RNA molecule

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Decoding the Information in DNA

• Translation

• Two types of RNA are used to read instructions on
  RNA molecule and put amino acids together to make
  the protein

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Decoding the Information in DNA

• Gene Expression

• Protein synthesis
• Protein making process based on information
  encoded in DNA

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TRANSCRIPTION

• Transcription

• Transfers info from a gene on DNA to RNA
• In prokaryotes- occurs in cytoplasm
• In eukaryotes- occurs in nucleus

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TRANSCRIPTION

• Transcription
• (STEPS)

• 1. RNA polymerase binds to start signal
  promoter on DNA
• 2. RNA polymerase unwinds and opens DNA double
  helix

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TRANSCRIPTION

• Transcription
• (STEPS)

• 3. RNA polymerase reads genes- adds and links
  matching nucleotides by base pairing (A-U and G-C)

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TRANSCRIPTION

• Transcription
• (STEPS)

• 4. RNA polymerase reaches stop signal at end of
  gene
• 5. As RNA polymerase works, a single strand of
  RNA grows

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TRANSCRIPTION

• Transcription
• (STEPS)

• 6. DNA helix zips itself back up as RNA
  polymerase passes by

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TRANSCRIPTION

• Transcription
• (STEPS)

• 7. Many identical RNA molecules are made
  simultaneously
• Feather like appearance in photos

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The GENETIC CODE

• Messenger RNA

• mRNA
• Made when cells need a protein made
• Delivers protein making instructions from gene to
  translation site
• Instructions written in codons

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The GENETIC CODE

• Codons

• Three nucleotide sequences along mRNA
• 64 possible codons
• Each corresponds to
• An amino acid OR
• A stop signal OR
• A start signal

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Can You Tell Me?

• 1. During DNA replication, what molecule reads
  the strand of DNA to make the matching strand?
• 2. During transcription, what molecule reads
  the DNA?
• 3. What material does the transcription process
  create?

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The GENETIC CODE

• RNAs role in translation

• Takes place in cytoplasm
• Transfer RNA (tRNA) and ribosomes help in protein
  synthesis

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The GENETIC CODE

• Transfer RNA

• tRNA
• Single strand, carries amino acid
• Folded shape
• Contains anticodon

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The GENETIC CODE

• Anticodon

• 3 nucleotides on tRNA that are complementary to a
  mRNA codon

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The GENETIC CODE

• Ribosomal RNA

• rRNA makes up part of ribosomes

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The GENETIC CODE

• Translation process

• 1. mRNA leaves nucleus, enters cytoplasm
• 2. Ribosome hooks onto mRNA at start codon

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The GENETIC CODE

• Translation process

• 3. tRNA attaches to ribosome subunit and binds
  to mRNA
• Anticodon of tRNA binds to codon of mRNA

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The GENETIC CODE

• Translation process

• 4. tRNA drops off amino acid its carrying
• 5. Another tRNA comes and drops an amino acid off

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The GENETIC CODE

• Translation process

• 6. Another tRNA enters, first tRNA leaves

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The GENETIC CODE

• Translation process

• 7. Each amino acid bonded to previous one to
  form a chain
• 8. tRNA detaches leaving
• amino acid attached to
• remaining tRNA

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The GENETIC CODE

• Translation process

• 9. Repeats until ribosomal subunit reaches stop
  codon
• 10. Newly made protein is released

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TRANSLATION
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TRANSLATION
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TRANSLATION
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TRANSLATION
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TRANSLATION
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Assessment One

• Distinguish two differences between RNA structure
  and DNA structure
• Explain how RNA is made during transcription
• Interpret the genetic code to determine the amino
  acid coded for by the codon CCU
• Compare the roles of the three different types of
  RNA during translation
• What is the maximum number of amino acids that
  could be coded for by a section of mRNA with the
  sequence GUUCAGAACUGU?

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Protein Synthesis

• Protein Synthesis in Prokaryotes

• Requires too much energy and too many materials
  for cell to make every protein encoded for by the
  DNA at all times
• Gene expression can be regulated according to
  cell needs
• Ex E. coli bacteria

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Regulating Protein Synthesis

• Lac Operon

• 1. Lactose in dairy products enters your
  intestines
• 2. E. coli there can use lactose for nutrition
  (to make glucose and galactose)

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Regulating Protein Synthesis

• Lac Operon

• 3. Three genes for breaking down lactose located
  next to each other on DNA (can turn them on or
  off)
• Genes on theyre ready to be transcribed and
  translated

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Regulating Protein Synthesis

• Lac Operon

• 4. These 3 genes turn on in presence of lactose
  and turn off in its absence

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Regulating Protein Synthesis

• Lac Operon

• 5. Operator- area on DNA (touching
  start/promoter) that acts as on and off switch
• Can block RNA polymerase from transcribing

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Regulating Protein Synthesis

• Lac Operon

• 6. Operon consists of
• Operator
• Promoter
• Three genes
• All work together to control lactose metabolism

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Regulating Protein Synthesis

• Lac Operon

• 7. No lactose present
• Lac operon is turned off when repressor protein
  binds to DNA
• Repressor blocks RNA polymerase from binding

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Regulating Protein Synthesis

• Lac Operon

• 8. In presence of lactose
• Lactose binds to repressor changing its shape
• Causes repressor to fall off DNA
• Allows RNA polymerase to bind and transcribe

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Regulating Protein Synthesis

• Protein synthesis in eukaryotes

• Most gene regulation is to control the onset of
  transcription (binding of RNA polymerase)

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Regulating Protein Synthesis

• Protein synthesis in eukaryotes

• Transcription Factors- regulatory proteins that
  help rearrange RNA polymerase into the correct
  position

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Intervening DNA

• Intervening DNA in Eukaryotic Genes

• 1. Introns- longs segments of nucleotides with
  no coding information
• Break up DNA/genes

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Intervening DNA

• Intervening DNA in Eukaryotic Genes

• 2. Exons- actual genes that are translated into
  proteins

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Intervening DNA

• Intervening DNA in Eukaryotic Genes

• 3. After transcription, introns in mRNA are cut
  out by spliceosomes
• Exons are stitched back together

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Intervening DNA

• Intervening DNA in Eukaryotic Genes

• 4. Large numbers of exons and introns allows
  evolutionary flexibility because they can be
  shuffled about to make new genetic codes

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Mutations

• Mutations

• Changes in DNA of a gene are rare
• When in body cells, only affect individual
• When in gametes, offspring can be affected

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Mutations

• Mutations

• A. Gene rearrangements- entire gene moved to a
  new location (disrupts its function)

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Mutations

• Mutations

• B. Gene alterations- changes a gene
• Usually results in wrong amino acid being hooked
  into protein (disrupts protein function)

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Mutations

• Mutations

• C. Point Mutation- single nucleotide changes

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Mutations

• Mutations

• D. Insertion Mutation- extra piece of DNA is
  inserted

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Mutations

• Mutations

• E. Deletion Mutation- segments of gene are lost

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Mutations

• Mutations

• F. Frame shift Mutations- causes gene to be read
  in wrong 3 nucleotide sequence
• Ex THE CAT ATE
• Remove C
• THE ATE TE (makes no sense)

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WEBSITES

• DNA Workshop
• Transcription
• Interactive Transcribing and Translating a Gene
• Protein Synthesis Animation
• Transcription Animation
• Translation Movie
• Protein Translation Animation
• Animation of Translation
• Protein Synthesis Movie
• Transcription Game
• Protein Synthesis Tutorial