Nucleic Acids and Protein Synthesis

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DNA, RNA And Protein Synthesis
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Modern Biology Pages 193 - 195
Function of DNA

• Structure of DNA must allow the storage and
  transmission of genetic information.

DNA spills from E. coli cell.
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Modern Biology Pages 193 - 195
Function of DNA
Genetic information must tell cell(s) how to
make proteins.
Proteins are made in the cytoplasm but DNA
remains in nucleus
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Modern Biology Pages 193 - 195
Functions of DNA
Proteins form structures and control chemistry of
cell.
Ribosomes embedded in the E.R. construct proteins
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Modern Biology Pages 193 - 195
Functions of DNA

• Structure of DNA must allow exact replication to
  occur.

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Why Understanding DNA is Important to You.
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DISCOVERY OF DNA GRIFFITHS EXPERIMENT
Modern Biology Pages 193 - 195

• Called transformation.
• Used mice and pneumonia.
• Rough (non-virulent)
• Smooth (virulent)

Griffiths Experiment
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Avery Determines DNA To Be Hereditary Molecule
Modern Biology Pages 193 - 195

• Avery, McCloud, and McCarty
• Used process of elimination.
• Determined DNA was heredity material.

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Important People in DNA Science
Modern Biology Pages 184 - 187

• Rosalind Franklin of Cal Tech in Los Angeles took
  pictures using X-Rays in the 1930s

Was never given due credit for her contribution
to DNA Science
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Important People in DNA Science
Modern Biology Pages 184 - 187

• James Watson Francis Crick discovered structure
  of DNA in 1953.

James Watson Left Francis Crick right Nobel
prize for DNA structure
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DNA Structure
Modern Biology Pages 184 - 187

• DNA is a polymer.
• The monomer of DNA is called a nucleotide.

deoxyribonucleic acid
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Nucleotide Structure
Modern Biology Pages 184 - 187

• One 5 carbon sugar called deoxyribose.
• Deoxy one less oxygen.
• ribo than ribose.
• Deoxyribonucleic acid
• nucleic found in nucleus.
• acid acidic

Deoxyribose, a pentose sugar, has each carbon
numbered.
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Nucleotide Structure
Modern Biology Pages 184 - 187

• Phosphate group attached to the 5 carbon of the
  sugar.
• The phosphoric acid is negative and so makes the
  DNA molecule negative.

The deoxyribose has a nitorgenous base and a
phoshate attached to it.
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Nucleotide Structure
Modern Biology Pages 187 - 189

• One nitrogenous base attached to the 1 carbon in
  the sugar..
• Adenine (Purine)
• Guanine (Purine)
• Cytosine (Pyrimidine)
• Thymine (Pyrimidine)

Four bases of DNA
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DNA Structure
Modern Biology Pages 187 - 189

• DNA molecule has shape of a double helix.
• The sides are anti-parallel.

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DNA Structure
Modern Biology Pages 187 - 189

• Nucleotides linked together form the sides of the
  DNA molecule.
• Phosphodiester bond links phosphates and
  deoxyribose

Each phosphate is linked to two sugar molecules.
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DNA Structure
Modern Biology Pages 187 - 189

• Complementary base pairing rules
• Nitrogenous bases form steps or rungs of the
  helix.
• Adenine (2 rings) is bonded with Thymine (1 ring)
  using 2 hydrogen bonds.
• Guanine (2 rings) is bonded with Cytosine (1
  ring) using 3 hydrogen bonds.

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CENTRAL DOGMA OF DNA
Modern Biology Pages 187 - 189

• DNA mRNA Protein

• DNA must send a message to ribosomes as to how a
  protein is to be produced.
• 2) DNA must replicate itself exactly prior to
  each cell division.

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Replication of DNA
Modern Biology Pages 187 - 189

• Replication must
• Occur prior to every cell division.
• Occur during S phase of interphase.
• Result in two identical copies of the DNA
  molecule.

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Replication of DNA
Modern Biology Pages 187 - 189

• DNA replication is semi-conservative
• Each new molecule is composed of one old and one
  new strand.

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Modern Biology Pages 187 - 189
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Replication Process
Modern Biology Pages 187 - 189

• Replication fork is where double helix is split
  apart.
• Double helix is split apart by enzyme called DNA
  Helicase.

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Replication Process
Modern Biology Pages 187 - 189

• Role of DNA polymerase.
• Constructs a new strand of DNA
• One side is continuous
• One side is discontinuous
• Complementary nature of bases allows replication
  to occur properly.
• Replication occurs at many sites at same time.

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Replication Process
Modern Biology Pages 187 - 189

• Mistakes and repair processes.
• Xeroderma Pigmentosa
• Lacks proper enzyme to repair DNA damage due to
  sunlight.

• Multiple carcinomas develop due to exposure to uV
  light

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RNA
Modern Biology Pages 190 - 194

• Structure of RNA.
• Ribose instead of deoxyribose.
• Uracil instead of thymine.
• Single helix instead of double.
• Three types of RNA.
• mRNA
• tRNA
• rRNA

RNA is made from DNA
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TRANSCRIPTION
Modern Biology Pages 190 - 194

• Making mRNA as a messenger.
• Process referred to as transcription.
• Purpose is to copy the message for a protein from
  the DNA molecule.

Making mRNA
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TRANSCRIPTION
Modern Biology Pages 190 - 194

• Transcription
• DNA untwists and unzips in area of molecule where
  the message for a certain protein is held.
• Role of RNA polymerase.
• Role of promoter.
• Role of termination signal.

Making mRNA
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TRANSCRIPTION
Modern Biology Pages 190 - 194

• The product of transcription is mRNA, tRNA,and
  rRNA.
• Transcription occurs in the nucleus of the cell.

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Translation
Modern Biology Pages 190 - 194

• Translation occurs in the cytoplasm.
• Amino acids are assembled polypeptides.
  (Proteins)
• Ribosomes assemble polypeptides based on
  instructions held in the DNA molecule.

mRNA leaving the nucleus
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Translation
Wednesday 1/8/03 Pages 194 - 198

• Protein structure
• Composed of building blocks called amino acids.
• 20 different types of amino acids.
• Sequence and length of amino acid chain
  determines the characteristics of the protein.

Ribosomes attach to the mRNA molecule in the
cytoplasm.
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Genetic code
Wednesday 1/8/03 Pages 194 - 198

• The Genetic Code
• Each 3 nucleotides on mRNA is a codon.
• Each codon codes for a specific amino acid.
• 64 possible codons.
• 1 start codons
• 3 stop codons
• 60 different codons code for 20 different types
  of amino acids.

mRNA codon list
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Wednesday 1/8/03 Pages 194 - 198
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Translation
Wednesday 1/8/03 Pages 194 - 198

• The ribosome binds to the mRNA.
• tRNA (with anticodon) brings proper amino acid to
  ribosome. (met tRNA)
• Ribosome moves to next three bases (codon).
• Another tRNA brings proper AA to ribosome.
• Protein is assembled.
• Stop codon signals end of protein.

tRNA brings an amino acid to the ribosome.