From Genes to Proteins

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From Genes to Proteins
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DNA and RNA differ in 3 ways

• RNA
• Single-stranded
• Ribose (sugar)
• Uracil (base) ? bonds to Adenine

• DNA
• Double-stranded
• Deoxiribose (sugar)
• Thymine (base) ? bonds to Adenine

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The Flow of Information
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The Flow of Information
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Transcription

• This is the first step in Protein Synthesis
• 1. The instructions are transferred
  (transcribed) to an RNA molecule.

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• To sum up Transcription
• Info transferred from DNA to RNA
• What is the Enzyme involved in Transcription?
• Answer ? RNA Polymerase

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Transcription has 3 steps

• 1 RNA Polymerase binds to the genes promoter
  (DNA) ? (like a starting line in a race).

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• 2 RNA Polymerase UNWINDS the DNA molecule. The
  DNA nucleotides are exposed.

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• 3 RNA Polymerase (yeah, that same enzyme
  again) adds complimentary nucleotides to
  separated DNA strand.
• Remember ? RNA has Uracil instead of Thymine
  for a base.

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• The RNA Polymerase will continue transcription
  until it reaches the stop signal on the DNA
  molecule (like a finish line).
• Then the RNA strand is released and goes on to
  the next stepTranslation

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Transcription
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Transcription
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3 types of RNA

• mRNA (messenger RNA)
• rRNA (ribosomal RNA)
• tRNA (transfer RNA)

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Messenger RNA

• Delivers information to the site of Translation.

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• mRNA instructions are written in
• 3-nucleotide sequences.
• These sequences are called codons.
• Ex. See pg. 209
• UUU, CUG, ACU, etc.
• There are 64 possible codons.

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Translation

• Remember what happens in Transcription?
• DNA to RNA
• In TranslationRNA is coded for Amino Acids.

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• Translation takes place in the Cytoplasm.
• tRNA (Transfer RNA) molecules carry single amino
  acids.
• They also have an OPPOSITE 3-nucleotide
  sequence called anticodons.

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• rRNA (Ribosomal RNA) molecules are like assembly
  lines ? they carry
• 1 mRNA
• 2 tRNA

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(No Transcript)
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7 Steps in Translation

• 1 mRNA start codon starts the process at the P
  site.
• 2 the next tRNA bonds to the next codon at the
  A site.
• 3 A P are holding 2 tRNAsa peptide bond is
  formed between 2 amino acids.

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• 4 tRNA detaches from P-site, leaves behind
  amino acid, leaves Ribosome.
• 5 tRNA at A-site moves to the P-site. Now a
  new codon is ready at the A-site for another
  tRNA.

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• 6 tRNA detaches from P-site, leaves behind
  amino acid, leaves ribosome.
• 7 (Steps 2 6 repeat until a stop codon is
  reached). Ex. UAG, UAA, UGA.
• A new protein is then released into the cell.

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Translation
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Translation