Download X – Ray Diffraction

What carries genetic information?
Agenda for Monday Oct. 25th
1. Intro DNA notes
2. Create DNA
Discovery of DNA
Griffith
• 2 strains of bacteria
– Smooth (pneumonia)
– Rough (no pneumonia)
• Conclusion
– Disease was passed
– One strain was
transformed into the
other
Discovery of DNA
Avery
• Isolated macromolecules of from killed S cells
– DNA, protein, lipids
• Found that living R cells exposed to S strain DNA
turned into S cells
• Conclusion
– DNA released
– R strain incorporated this DNA into its cells
Discovery of DNA
Hershey and Chase
• Bacteriophages – virus that attacks bacteria
– DNA and protein
– Viruses must inject DNA into living cell
• Labeled the both parts of virus (DNA and protein)
– Radioactive isotopes
– DNA – labeled phosphorous
– Proteins – labeled sulfur
Hershey and Chase Cont.
• Results
– Group 1: Labeled viral DNA in bacteria
– Group 2: Labeled proteins outside of bacteria cells
• Conclusion
– DNA provided genetic information needed to
produce new viruses
DNA
• Deoxyribose nucleic acid
• Macromolecule
• Store and transmit genetic
information
• Composed of smaller nucleotides
• Two types of nucleic acids: DNA
and RNA
Structure of DNA
Nucleotides – 3 parts
• 5 carbon sugar
– Deoxyribose
• Phosphate group
• Nitrogenous base
– A, T, C, G
Nitrogenous Bases
• 4 Bases
– Adenine (A), Thymine (T),
Cytosine (C), Guanine (G)
• Two types of bases
– Purine – Double ring bases
– Pyrimidine – single ring bases
Chargaff’s Rule
• Analyzed amount of each base in DNA
• Found the amount of guanine nearly equals
the amount of cytosine
– Amount of adenine nearly equals thyamine
• Chargaff’s rule:
C=G
A=T
Discovering Structure
of DNA
X – Ray Diffraction
• Maurice Wilkins and Rosalind
Franklin
• Photo 51
• Indicated DNA was a double helix
• http://www.pbs.org/wgbh/nova/ph
oto51/
Watson and Crick
• Saw Franklin’s Photo and used Chargaff’s data
– Built a model of DNA
– Published paper in 1953 suggesting structure of DNA
– Won Nobel Prize!
• Features of Model
1. Outside strands consist of alternating deoxyribose
and phosphate
2. C = G pair to each other with 3 hydrogen bonds
3. T = A pair to each other with 2 hydrogen bonds
Final Thoughts:
DNA
• Similar to a ladder
– Rails (outside of ladder)
are deoxyribose and
phosphate
– Base pairs are rungs of
ladder
– Twisted
Remember
DNA is like an Oreo
Phophates + sugars = cookies
Bases = cream filling
Final Thoughts:
DNA
• DNA is complementary
– Complementary: bases on one strand match up
with the bases on the other strand (A-T and G-C)
Example: Strand 1- ATG GGC CTA
Strand 2- TAC CCG GAT
What is a nucleotide made of (3
parts)?
Agenda for Tuesday Oct 26th
1. Finish DNA Notes
2. Create DNA
Orientation of DNA
• The nucleotides form a chain
• The phosphate end of the chain
is referred to as the 5' end. The
opposite end is the 3' end.
• Q: Since DNA is complementary,
what end matches with the 5’
end?
Timeline of Identifying Genetic
Material
• Genetic Material can Transform Bacteria Frederick Griffith, 1931
• The transforming material is DNA - Oswald
Avery, Colin MacLeod, and Maclyn McCarty,
1944
• More Evidence: The Genetic Material is DNA Alfred D. Hershey and Martha Chase, 1952
Timeline of Structure of DNA
• Erwin Chargaff, 1940’s and early 50's
• M.H.F. Wilkins and Rosalind Franklin, early
50’s
• James Watson and Francis H.C. Crick, 1953
What shape is DNA? How was this
discovered?
Agenda for Wednesday Oct 27th
1. Finish Making DNA
2. DNA Video
Remember!!
• 2 strands allow bases to pair
– A binds T with 2 H bonds
– C binds G with 3 H bonds
Phosphates +
sugars on the
outside
Bases on the
inside (Bases fit
like puzzle
pieces)
What is a purine? Pyrimidine? Give
an example of each.
Agenda for Thursday Oct. 28th
1. DNA models
2. DNA Review
3. DNA video
Info on Bases
• Purine – double ring base
– Guanine, Adenine
• Pyrimidine – single ring
base
– Cytosine, Thymine
Chromosome Structure
• Prokaryotes – DNA is in the shape of a ring
• Eukaryotic – chromosomes
– 51 – 245 million base pairs
– 5 centimeters
– Coils tightly around histones and forms nucleosome
– Nucleosome group together and form chromatin
fibers
– Chromatin fibers form chromosomes
Chromosome Structure
•DNA wraps around
histones
•8 histones
combine to form
nucleosome
Chromatin
Fibers
Histones
Nucleosomes
What does DNA stand for?
Agenda for Friday Oct 29th
1. Quiz
2. Review DNA sheet
3. Video
Person/People
Accomplishment and
Description
Year