1 Review How does a cell interpret the genetic code

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• 1 Review How does a cell interpret the genetic
  code
• Explain What are codons and anticodons
• 2 Review What happens during translation
• Compare and Contrast How is protein synthesis
  different from DNA replication
• 3 Review Why is the genetic code considered
  universal
• Infer In what way does controlling the
  proteins in an organism control its
  characteristics
• 4 Choose one component of translation. Write a
  question about that component and use it to form
  a hypothesis that could be tested in an experiment

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Ch 13 RNA and Protein Synthesis

• 13.2 Ribosomes and Protein Synthesis

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• Proteins are made from long chains of amino acids
  or polypeptides
• 20 different amino acids
• Order of amino acids make proteins different.

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Codon

• Each three-letter word in mRNA
• Consists of three consecutive bases that specify
  a single amino acid.

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How to Read Codons

• Four different bases in RNA, so 64 possible
  three-base codons (444 64)
• To read a codon, start at the middle of the
  circle and move outward.

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(No Transcript)
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• Starts with AUG
• Has three stop codons.

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Translation

• Decoding of an mRNA message into a protein
• From RNA to protein
• Different languages.

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Translation Steps

• mRNA is transcribed in the nucleus and then
  enters the cytoplasm for translation.

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• Ribosome attaches to an mRNA molecule
• Ribosome reads each codon of mRNA
• Directs tRNA to bring the specified amino acid
• Ribosome then attaches each amino acid to the
  growing chain.

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• tRNA has three unpaired bases or anticodon which
  is complementary to one mRNA codon
• Codon AUG
• Anticodon UAC.

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• Next codon is UUC
• tRNA molecule with an AAG anticodon brings the
  amino acid to ribosome.

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• Ribosome helps form a peptide bond between 1st
  and 2nd amino acid
• Bond between tRNA molecule and amino acid is
  broken
• tRNA shifts to 3rd site.

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• Ribosome moves over one codon
• New tRNA enters ribosome
• Process repeats itself.

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• Translation continues until a stop codon
• Ribosome release polypeptide and mRNA.

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Molecular Basis of Heredity

• Most genes contain instructions for assembling
  proteins.

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Proteins Can

• Be enzymes
• Produce pigment or odor
• Regulate growth
• Trigger development
• Operate cell parts.

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Gene Expression

• What DNA actually ends up doing
• How the genes gets expressed or shown.

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• Genetic code is nearly universal in all living
  organisms.

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• A certain gene has the following base sequence
  GACAAGTCCACAATC
• Write this sequence down
• From left to right, write the sequence of mRNA
  molecule transcribed from this gene
• Using the figure on pg. 311, read the mRNA from
  left to right and write down the amino acid
  sequence
• Repeat step 3 reading the codons from right to
  left.

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Analyze and Conclude

1. Apply Concepts Why did steps 3 and 4 produce
   different polypeptides
2. Infer Do cells usually decode nucleotides in one
   direction only or in either direction