Lec 17 Flashcards
Friedrich Miescher
First Isolated DNA from white blood cells and called in nucleon
-noted that it was slightly acidic and high in phosphorus
Albrecht Kossel
DNA has 4 nitrogenous bases (adenine, guanine, cytosine and thymine)
Phoebus Levene
DNA is made of nucleotides
-with each nucleotide having a base sugar and phosphate
Purines
Adenine and Guanine
Pyrimidine
Cytosine
Thymine
Uracil
4 nitrogenous bases of DNA
Adenine, Guanine, cytosine, and thymine
4 nitrogenous bases of RNA
Adenine, Guanine, Cytosine, and Uracil
Know structure of Purines and Pyrimidines
look in lec. 17
Difference between deoxyribose and ribose?
Deoxyribose is missing the oxygen on the 2’ Carbon
Nucleoside
sugar+base
Nucleotide
Sugar + base + phosphate
nucleoside monophosphate
is another name for nucleotide
nucleotide triphosphate
sugar + base + 3 phosphates
Who proposed the tetra nucleotide structure of DNA? and what was the genetic material thought to be back then?
Phoebus Levene and the genetic material was thought to be protein
Griffeth
OBSERVED Transformation
- cells did not need to be injected into a mouse in order to get transformation. Transformation could occur if heat-killed smooth cells were mixed in a test tube with non virulent cells
- transformation can be accomplished by incubating the filtrate from heat killed cells with nonvirulent cells showing that intact virulent cells were not required for transformation.
**heat-killed S-cells do not cause death
Avery, MacLeod and McCarty
DNA is the “transforming principle”
Hershey and Chase
Showed that DNA holds the genetic information, not protein, through their experiment of following the tract of protein and DNA in phages through isotopes.
Yanofsky
Studied Tryptophan synthetase genes and proteins
-established that changes in DNA and protein were collinear
Heinz Äraenkel-Conrat and Bea Singer
looked at two strains to determine if genetic material was RNA or protein. Virus particles were type A which was RNA
THUS proved RNA was the genetic material in RNA virus
Maurice Wilkins and Rosalind Franklin
X-ray Diffraction Studies
-results in famous picture of DNA and showed that DNA was a Helix
Erwin Chargraff
Base composition studies
Concluded:
1 A=T and G=C
2 A+G=T+C from (A+G)/(T+C)=1
Watson and Crick
Model for DNA structure (determined the structure)
-base paring between two strands of nucleotides allows for content width of helix and agrees with charges base composition rules
Phosphodiester bonds
join sugar-phosphate backbone
Is DNA positive or negatively charged?
negative
What nucleotides are complementary to each other in DNA?
A-T
G-C
How many hydrogen bonds are between a Adenine and Thymine?
2 hydrogen bonds
Hydrogen bonds
are relatively weak attractions between positively and negatively charge molecules. They are NOT the main force joining the two strands of DNA
How many hydrogen bonds are between Guanine and Cytosine?
3 hydrogen bonds
Plectonic coil?
Needs to unwind to separate the two strands
What is the main force in stabilizing the double helix?
Hydrophobic interactions (maximized by base stacking)
Where are the hydrophobic bases located on the double helix?
in the center
Where is the hydrophilic backbone located on the helix?
on the outside
