1 Chapter 9 DNA: The Molecule of Heredity What is DNA? Answer: Molecule that carries the blueprint of life General Features: • DNA is packages in chromosomes (DNA + Proteins) • Gene = Functional segment of DNA located at a particular place on a chromosome Gene Chromosome Discovery of nucleic acid • 1869: Miescher isolated DNA from pus! • DNA is made up of: Deoxyribose : the sugar Phosphate nitrogen rich base
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Biol102 Chapter 9 - Western Oregon University › ~kissanek › Handouts › Handouts › 3_Biol102_Chapte… · 2008-11-06 · as templates • Parental strand and new daughter strand
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1
Chapter 9
DNA: The Molecule of Heredity
What is DNA?
Answer: Molecule that carries the blueprint of life
General Features:
• DNA is packages in chromosomes (DNA + Proteins)
• Gene = Functional segment of DNA located at a particular place on a chromosome
Ge
ne
Chromosome
Discovery of nucleic acid
• 1869: Miescher
�isolated DNA from pus!
• DNA is made up of:
�Deoxyribose : the sugar
�Phosphate
�nitrogen rich base
2
What is the genetic material?
• Protein vs DNA
�Debated until the 1950’s.
• Protein complex
�20 different amino acids
�Forms thousands of different
molecules.
• DNA simple
�Only 4 nucleotides
Lactase
Genetic material = DNA
• Two major experiments
� 1920’s -1950’s
1. Griffith’s dead mice
2. Radioactively labelledbacteriophages
� Bacteriophages are viruses that destroy bacteria. Typical bacteriophage
infecting a bacteria cell
Griffith’s mice experiment
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(Figure 9.1)
Second experiment: radioactive viruses
• Viruses have protein coats, which
enclose DNA or RNA.
�Only DNA viruses was used in this
experiment.
• The proteins were labelled with
radioactive sulfur, the DNA was
labelled with radioactive
phosphorus.
Electron microscope
photos of bacteriophages.
virus particlelabeled with 35S
DNA (blue)being injected
into bacterium
35S remainsoutside cells
virus particle
labeled with 32P
DNA (blue)
being injected into bacterium
35P remains
inside cells
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Structure of DNA:
• Nucleic acid composed of individual nucleotides
Deoxyribose
Know this structure, you will see it on the exam!
Structure of DNA:
• 4 types of nucleotides (nitrogen base differences):