DNA The Code of Life

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DNAThe Code of Life
The Molecular Basis of Inheritance
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History
Search for genetic material 1928 Frederick
Griffith transforming principle
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History
Search for genetic material Bacteria and
viruses also have DNA
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History
Search for genetic material 1952 -
Hershey-Chase Experiment
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History
Search for genetic material

• Classic experiments for evidence Griffith
  transformation Hershey-Chase DNA necessary
  to produce more virus
• Other supporting evidence DNA volume doubles
  before cells divide Chargaff ratio of
  nucleotides A T and G C

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History
Search for genetic material James Watson and
Francis Crick used this photo with other evidence
to describe the structure of DNA.
X-ray diffraction photo of DNA Image produced by
Rosalind Franklin
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History
Search for genetic material Watson and Crick
with their DNA model
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Structure
Basic structure of DNA is a sugar-phosphate
backbone with 4 variable nitrogenous bases.
This structure is called a nucleotide.
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Structure
There are 4 different nucleotides in DNA
Adenine pairs with Thymine Guanine pairs with
Cytosine
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Structure
Adenine pairs with Thymine Guanine pairs with
Cytosine
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Structure
Does DNA fit the requirements of a hereditary
material?
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Replication
Before replication, the parent DNA molecule has 2
complementary strands
First the 2 strands separate
Each old strand serves as a template to
determine the order of the nucleotides in the new
strand
Nucleotides are connected to form the backbone
now have 2 identical DNA molecules.
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Replication
DNA Replication is simple, but it takes a large
team of enzymes and proteins to carry out the
process

• Helicase unwinds the molecule
• Single-strand binding protein stabilized ssDNA
• Primase initiates the replication with RNA
• DNA polymerase extends the new DNA
• Second DNA polymerase removes the RNA
• DNA ligase joins all the fragments

Click on the small helix to watch animated
replication
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Extraction
Each human cell has enough DNA to code for all
the traits in the human body. If the DNA in one
cell was stretched out, how long would it be? Do
the math! There are 6 X 109 base
pairs/cell Each base pair is 0.34 X 10-9 meters
long
Answer 2 meters
A human body has approximately 75 trillion cells.
If the distance to the sun is 150 X 109 meters,
how many round trips could your DNA make?
Answer 500 trips
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Extraction
DNA from kiwi fruit