Flashcards in Chapter 8 Definitions/Concepts Deck (42)
Adenine and Guanine
Cytosine, Thymine and Uracil.
Minor Nitrogenous Bases
Ribose, found in DNA subjected to oxidative damage.
Found in beta Furanose form.
Place C1' and C4' in the same plane with the nitrogen up. Up is endo, down is exo.
Forms 3'-5' bond between nucleotides.
RNA Alkaline Hydrolysis
RNA is susceptible to non-enzymatic hydrolysis in alkaline conditions because of the 2'-hydroxyl group.
Nucleotide Base Properties (6)
1. Weakly basic.
2. Highly Conjugated/ Planar
3. Absorb UV light around 260nm.
4. Free bases are very hydrophobic and insoluble at physiological pH.
5. Bases stack antiparallel to minimized hydrophobic surfaces due to pi interactions.
6. Ring nitrogens, carbonyl groups, and exocyclic amino groups form hydrogen bonds with other bases.
Watson and Crick Basepairs
G-C has 3 hydrogen bonds
A-T has 2 hydrogen bonds
First isolated DNA in 1868. He originally called it nuclein. It consisted of an acidic portion (DNA) and basic portion (protein).
Avery, McLeod and McCarthy
1944 extracted DNA from a virulent strain of strep pneumonia and transformed a non-virulent strain into a virulent strain.
Hershey and Chase
1952 radioactively labeled P viral DNA that enters a host cell and provides genetic information for viral replication whereas S viral protein doesn't enter the cell.
1940's established the base composition rules.
-varies across species
-constant across tissues
-constant through age
-shows amounts of A=T and C=G
1951 first crystal structure of cytidine nucleoside. Used this info to start building structure because it gave bond angles.
Dekker, Michelson and Todd
Early 1950's established the 3'-5' phosphodiester linkage
Electromagnetic titration found hydrogen bond linkage in 1947.
Fiber x-ray diffraction hinted at base stacking in 1947.
Rosalind Franklin and Maurice Wilkins
Analyzed DNA fibers with x-ray diffraction and were able to interpret results in 1953.
-Franklin found 2 strands
-Phosphate groups on the outside
-2 forms of DNA
-3.4A and 34A
Watson and Crick
Put the pieces from Franklin and Wilkins together in 1953. They found base pairing with the correct tautomer, 2 anti-parallel strands, base paired and helical with 10 nucleotides per turn.
1962 Nobel Prize
Wilkins, Perutz, Crick, Steinbeck, Watson and Kendrew.
Characteristics Causing Conformational Variability
1. Ribose Conformation
2. Backbone Bond Rotations (5 bonds)
3. Glycosidic Bond Rotation (between sugar and anything else)
DNA Conformational Variability
Function of binding protein
-shorter and fatter turns
-high bp tilt
-tall and thin turns
-low bp tilt
-C2' endo and C3' endo
T-A and C-G are found opposite each other on the helix.