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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 ... – PowerPoint PPT presentation

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Title: 1 Review How does a cell interpret the genetic code


1
  • 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

2
Ch 13 RNA and Protein Synthesis
  • 13.2 Ribosomes and Protein Synthesis

3
  • Proteins are made from long chains of amino acids
    or polypeptides
  • 20 different amino acids
  • Order of amino acids make proteins different.

4
Codon
  • Each three-letter word in mRNA
  • Consists of three consecutive bases that specify
    a single amino acid.

5
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.

6
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7
  • Starts with AUG
  • Has three stop codons.

8
Translation
  • Decoding of an mRNA message into a protein
  • From RNA to protein
  • Different languages.

9
Translation Steps
  • mRNA is transcribed in the nucleus and then
    enters the cytoplasm for translation.

10
  • 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.

11
  • tRNA has three unpaired bases or anticodon which
    is complementary to one mRNA codon
  • Codon AUG
  • Anticodon UAC.

12
  • Next codon is UUC
  • tRNA molecule with an AAG anticodon brings the
    amino acid to ribosome.

13
  • 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.

14
  • Ribosome moves over one codon
  • New tRNA enters ribosome
  • Process repeats itself.

15
  • Translation continues until a stop codon
  • Ribosome release polypeptide and mRNA.

16
Molecular Basis of Heredity
  • Most genes contain instructions for assembling
    proteins.

17
Proteins Can
  • Be enzymes
  • Produce pigment or odor
  • Regulate growth
  • Trigger development
  • Operate cell parts.

18
Gene Expression
  • What DNA actually ends up doing
  • How the genes gets expressed or shown.

19
  • Genetic code is nearly universal in all living
    organisms.

20
  • 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.

21
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
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