Download nitrogen bases.

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January 7, 2015
 Objectives:
 To
understand how DNA was discovered
 To be able to model the structure of DNA
 Journal:
Do you think that people have always known
that DNA carries our genes? How do you
think it may have been discovered?
*** Hand in Race for DNA Structure
Worksheet
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The Discovery of DNA
Before
the 1950s, scientists
weren’t sure what genes were
made of
There
was a race between the
best scientists in the world to
figure it out
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Experiments that Determined DNA was
the Genetic Material in Cells
 Griffith’s
Discovery of Transformation
 Discovered that genetic material could be
transferred between cells
 Hershey-Chase
Experiment
 Determined that DNA is the hereditary
material instead of proteins
 Rosalind
Franklin and Maurice Wilkins
 Took pictures of DNA using x-ray diffraction
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Experiments that Determined the
Structure of DNA
 Chargaff
 Determined
amount of A = T,
C=G
 James Watson
and Francis
Crick
 Built model of DNA
 Credited with actually
discovering DNA structure
Function of DNA
 Contains the information on how
to make proteins.
 Proteins are the workers to put
together and run a cell.
Building blocks of DNA
Nucleotide Structure – basic building
block of DNA
Sugar
Phosphate Group
Nitrogen Base
P
Sugar
N. Base
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Four Different Nitrogen Bases
1. Adenine
2. Guanine
3. Thyamine
4. Cytosine
DNA Structure
•Double
Stranded Helix
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Antiparallel Strands
 DNA
strands run antiparallel, opposite of each
other
 One
runs from 5’ to 3’ the other runs from 3’ to 5’
Spiral Staircase
Structure
Sides
of the staircase =
sugar & phosphates
 Steps of the staircase =
nitrogen bases.
Base Pairing Rule:
A – T held together by two hydrogen bonds
C – G held together by three hydrogen bonds
Purines vs. Pyrimidines
 Purines
 Structure
has two rings
 Adenine and Guanine
 Pyrimindines
 Structure
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has one ring
Cytosine and Thymine
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The Race for DNA Structure Video
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https://www.youtube.com/watch?v=d7ET4bbkTm0