DNA Review

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DNA Review

• The nucleotide bases will point to the inside of
  the DNA molecule while the outside (backbone) of
  the DNA molecule will be made of the sugar and
  phosphate molecules
• When complete the DNA molecule forms a double
  helix (two spiral sides wrapped together)

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CHROMOSOMES CONTAIN DNA

• The nucleus contains chromatin
• Chromatin is made of smaller nucleosomes
• A nucleosome is formed by a DNA molecule wrapped
  around a protein stick
• Looks like cotton candy wrapped around the paper
  cone

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Protein Synthesis
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Why is it important?

• Cells are controlled by enzymes- enzymes are
  proteins
• Almost every substance made by the cell is or
  contains a stuctural protein

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Vocabulary

• Gene- a portion of DNA that codes for a protein-
  the recipe for a protein
• mRNA- messenger RNA
• tRNA- transfer RNA- transfers amino acids
• Codon- mRNAs complementary trio of bases
• Anticodon- tRNAs complementary trio of bases
• Transcription- mRNA making a template of DNAs
  code
• Translation- tRNA reading mRNAs code and
  transferring the amino acids necessary to form a
  protein

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Two Steps to Protein Synthesis

• Transcription- takes place in the nucleus-mRNA
  makes template of DNAs code
• Translation- takes place on the ribosome in the
  cytoplasm- tRNA transfers amino acids

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Things to Remember

• DNA contains the recipes for proteins- called
  genes
• DNA is made of the bases adenine, thymine,
  guanine and cytosine
• A-T and C-G
• RNA is made of the bases adenine, uracil, guanine
  and cytosine
• A-U and C-G

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Transcription

• Takes place in the nucleus
• DNA unzips
• mRNA makes a template of the DNA code
• mRNA copies the code three bases at a time- this
  is a codon

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Transcription- mRNA forms codons
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Translation- on the ribosome, tRNA transfers
amino acids
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Another Look
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Another View
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The four bases can combine in 64 different
triplicate (codon) combinations

• Each codon codes for a specific amino acid

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Codon Chart
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Another Codon Chart
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Protein Structure
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A Few of The Finished Products! Proteins
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Think About It-

• Letters? Words? Sentences
• Sam hit the ball.
• Bases? Amino Acids? Proteins

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View It!

• http//www.wisc-online.com/objects/index_tj.asp?ob
  jIDAP1302
• http//www.pbs.org/wgbh/aso/tryit/dna/shockwave.ht
  ml

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Wrap Up

• 1. DNA message is transcribed into messenger RNA
  (mRNA)
• 2. mRNA leaves the nucleus and attaches to a
  ribosome
• 3. Each three letter codon will attract a
  matching three letter anti-codon of transfer RNA
  (tRNA)
• 4. Each tRNA is carrying an amino acid on its
  back
• 5. As the tRNA molecules line up, their amino
  acids also line up
• 6. As the amino acids are lined up, they
  chemically bond to form a protein

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Mutations- Any error in the genetic code

• Can happen when
• DNA is making new copies of itself (replication)
• DNA is being used to make messenger RNA
  (transcription)
• Transfer RNA is being attracted to the messenger
  RNA at the ribosome (translation)

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Types of Mutations

• Point mutations happen when one or two bases are
  different than they are supposed to be
• Frameshift mutations happen when extra bases are
  added or deleted

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