DNA Structure Flashcards
(23 cards)
What year was the Nobel Prize given for the discovery of DNA structure?
1953
Who won the Nobel Prize for discovering the structure of DNA?
James Watson
Francis Crick
Maurice Wilkins
Who actually got the evidence on the structure of DNA and had her research stolen?
Rosalind Franklin
What is the difference between a nucleoside and a nucleotide?
Nucleoside = base bound to sugar Nucleotide = base bound to sugar and phosphate
What is the bond between the sugar and the base?
glycosidic bond
What is the bond between the phosphate group and the sugar-base?
phosphoester bond
What is the name of the stand alone sugar in DNA?
2’ - deoxyribose
What rxn is taking place to combine phosphoric acid, 2’ -deoxyribose, and the base into a nucleotide?
dehydration reaction
Who discover base pairings and how?
Erwin Chargaff
Tested molar ratios of bases and found equivalent amounts of guanine to cytosine and adenine to thymine.
What bond makes up the DNA backbone of each strand?
Phosphodiester linkage
What does it mean when the 2 DNA strands run 5’ to 3’ and the other 3’ to 5’?
The 2 strands run anti-parallel to each other.
What is the difference between a purine and a pyrimidine?
Purine = 5 member ring + 6 member ring (larger) Pyrimidine = 6 member ring (smaller)
What are the purines?
Guanine and Adenine
What are the pyrimidines?
Cytosine and Thymine
What are the 4 bases?
Guanine
Thymine
Cytosine
Adenine
What are the complimentary bases and how many bonds do they form?
Guanine to Cytosine = 3 H bonds
Adenine to Thymine = 2 H bonds
What are the tautomeric states?
Pyrimidines = Amino Imino Purine = Keto Enol
Which tautomeric states are in major access at equilibrium?
Amino and Keto
Why are tautomeric states important?
The minor forms can be a large source of mutations due to inappropriate bonds forming.
What are the 3 ways the double helix is stabilized?
- Hydrogen bond pairing
- Base stacking
- Phosphate backbone
How are Hydrogen bond pairing and base stacking important to double helix stabilization?
Both create a hydrophobic environment. H2O is displaced by the hydrogen bond pairing
The base stacking is hydrophobic when in the double stranded formation and the planar bases stack on top of each other to exclude water.
Without water, the reactivity lowers (increased entropy) within in the internal environment.
How does the phosphate backbones stabilize the double helix?
The phosphate backbone is hydrophilic with charges in the aqueous solution which stabilizes the hydrophobic rxns internally.
Is the double helix right-handed or left handed?
The most common form of DNA is DNA B which exists in aqueous solutions. This form is right-handed.
