Discovery of DNA and DNA Structure

1
Discovery of DNA andDNA Structure

• 10/31/07

2
Bell Work

• 1. Define
• Bacteriophage
• Nucleotide
• Nitrogenous base
• Purine
• Pyrimidine

3
CA Standards

• 1. The fundamental life processes of plants and
  animals depend on a variety of chemical reactions
  that occur in specialized areas of the organism's
  cells. As a basis for understanding this concept
• c. Students know how prokaryotic cells,
  eukaryotic cells (including those from plants and
  animals), and viruses differ in complexity and
  general structure.

4
ELD Standard

• Use a dictionary to find a new words meaning.

5
Objectives

• Describe the basic differences of viruses,
  bacteria, and eukaryotic cells.
• Trace how viruses, bacteria, and eukaryotic cells
  were used by Griffith, Avery, and Hershey and
  Chase in their experiments.
• Describe the 3 parts of a nucleotide.

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Bacteria, Virus, or Eukaryote?

• Bacteria Prokaryote that usually have a cell
  wall and usually reproduce by cell division.

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Bacteria, Virus, or Eukaryote?

• Virus A nonliving, infectious particle composed
  of a nucleic acid and a protein coat. It can
  invade and destroy a cell.

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Bacteria, Virus, or Eukaryote?

• Eukaryote An organism made of cells that have a
  nucleus enclosed with a membrane, multiple
  chromosomes, and a mitotic cycle.

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Griffiths Experiments

• Studied Streptococcus pneumoniae
• Tried to make a vaccine against the virulent,
  disease causing strain of the bacterium.
• Virulent strain has a smooth capsule and is
  called the S strain.

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Griffiths Experiments

• Nonvirulent strain has no capsule and grows in
  rough colonies is called the
• R strain.

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Trace Griffiths Experiments
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Transformation

• trans meaning across
• Forma meaning a form
• Definition
• To change the condition, character, or function
  of something.

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Averys Experiments

• To test whether the transforming agent in
  Griffiths experiments was DNA or RNA.
• Enzymes used to destroy DNA, RNA, and proteins in
  heat killed S cells.
• 1st Used a protease enzyme to destroy protein.
• 2nd Used RNase enzyme to destroy RNA.
• 3rd Used DNase enzyme to destroy DNA.

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Averys Experiments

• Mixed the three experimental batches of
  heat-killed S cells with live R cells and
  injected mice with the mixtures.
• Cells from 1st transformed R cells into S cells.
• Cells from 2nd transformed R cells into S cells.
• Cells from 3rd did not transform R cells into S
  cells and the mice survived.

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Cells from 1st transformed R cells into S cells.

• Conclusion
• DNA is responsible for transformation in bacteria.

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Hershey-Chase Experiment

• Tested whether DNA or protein was the hereditary
  material that viruses transfer when viruses enter
  a bacterium.
• Definition Bacteriophage (phages)
• Virus that infects bacteria.

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Hershey-Chase Experiment
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Hershey-Chase Experiment

• Conclusion
• DNA is the hereditary molecule in viruses.

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Day 2 Ch. 10 Bell Work

• What is meant by virulent?
• Trace Griffiths experiment.

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CA Standards

• 4. Genes are a set of instructions encoded in the
  DNA sequence of each organism that specify the
  sequence of amino acids in proteins
  characteristic of that organism.
• b. Students know how to apply the genetic coding
  rules to predict the sequence of amino acids from
  a sequence of codons in RNA.

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DNA

• The material that contains the information that
  determines inherited characteristics.
• The primary function of DNA is to store and
  transmit genetic information.

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DNA Structure
Double Helix spiral staircase
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DNA Structure

• Discovered by Watson and Crick in 1953
• Rosalind Franklin took an xray photograph of DNA
  crystals that confirmed the structure proposed by
  Watson and Crick.

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DNA Structure

• Nucleotide Subunits that repeat to make a
  nucleic acid.
• Consists of 3 parts
• Five-carbon sugar in DNA its deoxyribose
• Phosphate group P 4 oxygen atoms
• Nitrogenous base contains nitrogen, carbon and
  is a base (accepts H ions)

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Nitrogenous Bases

• The sugar and phosphate group are identical in
  all DNA nucleotides.

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Nitrogenous Bases

• There are 4 nitrogenous bases
• Thymine (T) Pyrimidine single ring
• Cytosine (C) Pyrimidine single ring
• Adenine (A) Purine double ring
• Guanine (G) Purine double ring

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Complementary Bases

• Bases pair by Base-Pairing Rules
• In DNA Complementary Base Pairs are
• Cytosine pairs with guanine
• Adenine pairs with thymine

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Complementary Bases

• Base sequence the order of nitrogenous bases on
  a chain of DNA.
• Important for 2 reasons
• The hydrogen bonds between the base pairs help
  hold the two strands of a DNA molecule together.
• The complementary nature of DNA helps explain how
  DNA replicates before a cell divides. (One strand
  can serve as a template)

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DNA Models
A C C T G T G A G A C T G G A C A
C T C T A