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33 Cards in this Set
- Front
- Back
James Watson and Francis Crick
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Informally learned about Franklin's result before they were published in 1953, quickly worked out a likely structure of DNA molecule. Never actually performed their own experiments for DNA but used available info to produce models
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Rosalind Franklin
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British chemist who used X-ray diffraction technique to analyze DNA
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Maurice Wilkins
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Another researcher working in same lab as Franklin, was able to prepare more uniformly oriented DNA fibers than anyone else at the time. Franklin used these to obtain crude diffraction info on natural DNA. Suggested that DNA is in the shape of a helix
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Linus Pauling
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-American chemist
-Double nobel prize winner -Looked for structures of many molecules using ball and stick models -Worked too quickly and created the wrong model, giving W/C another chance |
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x-ray crystallography
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-Crystal form of DNA
-Light hits crystals to form regular pattern -First clue to structure |
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Erwin Chargaff
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-Expert in chemistry of NA
-Explained to W/C the rules of chemistry of DNA -Pairs AT, GC -First clue to structure |
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Ball and stick models
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-Used by Watson and Crick and Linus Pauling
-W/C chose to build models (minimum data) instead of crystallography -Linus Pauling used the models to look for the structures of many molecules |
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X pattern
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The X pattern on the x-ray diffraction photograph of DNA fibers made in 1953 by Rosalind Franklin was interpreted to show the double helical structure of DNA.
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Nucleotide
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Compound consisting of a nucleotide linked to a phosphate group. They form the basic structural unit of DNA and RNA.
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Deoxyribonucleic acid
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-3 main components
1) 5 carbon sugar with OH group attached to 3' sugar 2) Phosphate group (PO4) attached to (C5) 5' 3)Nitrogenous base group -Made up of nucleotides attached to form chain (strand) and connected by hydrogen bonding between the nitrogenous bases |
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Ribonucleic acid
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-3 main components
1) 5 carbon sugar with OH group attached to 3' sugar 2) Phosphate group (PO4) attached to (C5) 5' 3)Nitrogenous base group |
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Five carbon sugar
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The nucleotide subunits of DNA and RNA are composed of this
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Phosphate group
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Attached to a five carbon sugar in a nucleotide subunit on 5' or the fifth carbon. Connects with OH group of another nucleotide subunit
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Nitrogenous base
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Purine or pyrimidine
ACTG |
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5', 3', 1'
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5' end connects with Phosphate group
3' end connects with OH group 1' connects with complementary nitrogenous base |
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Phosphodiester bond
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linkage of 5' phosphate and 3' hydroxyl group which are linked to the two sugars by ester bonds. Many thousands of nucleotides can join together via these linkages to form long nucleic acid polymers
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Adenine
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Nitrogenous base that pairs with Thymine to form the DNA structure.
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Guanine
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Nitrogenous base that pairs with Cytosine to form the DNA structure.
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Cytosine
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Nitrogenous base that pairs with Guanine to form the DNA structure.
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Thymine
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Nitrogenous base that pairs with Adenine to form the DNA structure.
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Uracil
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Nitrogenous base that forms complementary bond with Adenine in the mRNA strand. Replaces T
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Double helix
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Key to the model was figured out by W/C that each strand is made up of two chains of nucleotides that are intertwined
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Phosphodiester backbone
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Strand of nucleotides, sequence varies
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Antiparallel
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The two strands of DNA connect to each other one running 5' to 3', the other 3' to 5'
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Complementary
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Complementary base pairing occurs by double bonding between A and T and triple bonding between C and T
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Who were the groups of scientists involved in the race to discover the structure of DNA?
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Watson and Crick (Cambridge)
Rosalind Franklin and Maurice Wilkins (King's College) Linus Pauling Erwin Chargaff helped W/C |
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How did the scientific approaches of these groups differ?
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Watson and Crick used a carefree approach and the ball and stick models that Linus Pauling also used.
Rosalind Franklin and Maurice Wilkins used X-ray crystallography. Erwin Chargaff used his expert knowledge of chemistry to predict the DNA structure |
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Purines
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Bigger than Pyrimidines
Adenine Thymine |
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Pyrimidines
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Smaller than purines
Cytosine Guanine |
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How did personality and competition get in the way of discovery?
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Most personality issues occurred between Franklin and Wilkins who worked in the same lab but didn't collaborate. Watson and Crick used questionable methods to obtain the info that led them to their discoveries and Linus Pauling used his fast and arguably overconfident technique hoping to be the first to discover the structure.
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How did Wilkin's "let the cat out of the bag?"
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Wilkins showed Watson the photograph that Franklin had obtained through X-ray crystallography which led W/C to use their other info to determine the DNA structure.
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Describe how Watson used Chargaff's and Franklin's data to develop a DNA model on February 28, 1953.
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-Knowing that 4 chemicals join in pairs
-The shape would lead to the function of the molecule -Used Cardboard models to show that -2 base pairs were identical in shape -Stacked on top of each other and twisted around |
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How does complementarity hold the backbones of the double helix together?
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The hydrogen bonding holds the double stranded DNA together by hydrogen bonds in which A forms 2 bonds with T and C forms 3 bonds with G.
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