DNA Transcription and Translation

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DNA Transcription and Translation

• How are proteins made from the DNA code

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Components of DNA

• Nucleotide nitrogenous base
• 5-carbon sugar
• phosphate

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Protein Synthesis

• The purpose of DNA is to code for proteins. To
  do this, the cell needs RNA
• What is RNA?

DNA RNA
deoxyribonucleic acid ribonucleic acid
sugar is deoxyribose sugar is ribose
double stranded single stranded
contains thymine contains uracil
1 type 3 types
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Types of RNA

• Messenger RNA (mRNA) carries the DNA message
  from nucleus to the rest of the cell

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Types of RNA

• Ribosomal RNA (rRNA) ribosomes, where proteins
  are assembled, are made of RNA

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Types of RNA

• Transfer RNA (tRNA) transfers amino acids
  (components that make up proteins) to the
  ribosome where they are assembled into a protein
  chain

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Putting it all together 1
Transcription

• DNA is unwound and a copy is made first it is
  made into an RNA strand

Similar to figure 12.14 in text
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Promoters

• How does cell know where to start transcribing
  DNA into RNA (and where to stop)?
• There are start areas called promoters and
  stop areas

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2 Editing

• Pieces of the RNA (introns) are removed and then
  it is reassembled with just the exons
• (There is much research and debate over the
  purpose and evolutionary significance of introns.
  One observation is that the larger the species,
  the more introns.)

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3 Translation

• RNA needs to be translated into amino acids.
  Amino acids are then strung together and
• Voila! A protein is made!
• (Ok, but its kind of complicated)

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The Genetic Code

• Proteins are made by joining amino acids into
  strands called polypeptides
• There are 20 different amino acids
• Genetic code is read in groups of 3 bases
• Each group of 3 bases is a codon
• Each codon corresponds to an amino acid

Fig. 12.17 in text
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How to use the code

• Glycine is coded for by GGU, GGC, GGA, or GGG

See glycine again here? (a different way to show
the same code)
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Try to translate this code

• Use Fig 12.17 in text
• AUGUCUCGACGUGGGUAG
• Start, Serine, Arginine, Arginine, Glycine, Stop
• AUGUCUCGACGUGGGUAG

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• Video of transcription and translation