DNA Flashcards
How many rings do purine and pyrimidine have
Purine is 9 membered and pyrimidine is 6 membered
What are the chemical name of all the nitrogenous bases
Adenine - 6 aminopurine
Guanine - 6 oxy 2 aminopurine
Cytosine - 2 oxy 4 aminopyrimidine
Thymine - 5 methyl 2,4-dioxypyrimidine
Characteristics of nitrogenous bases
They are heterocyclic structure, planer, aromatic and insoluble in water.
What kind of sugar pucker found in DNA
A DNA - C3
B DNA - C2
Z DNA - C2 & C3
Sugar and nitrogenous bases are joined by which carbon atom and nitrogen atom
Carbon 1
Pyrimidine N1
Purine N9
Nucleoside joined to phosphate group by which carbon atom
C5
Chargaff’s Rule
%A = %T, %G = %C
Molar ratio A to T and G to C equals 1
Sum of purine equals to sum of pyrimidine
Percentage of C plus G isn’t equal to A plus T
Who gave DNA double helix model and x ray diffraction data of DNA fibres
Double helix - Watson and Crick
X Ray - Franklin and Wilkins
What is at the core and periphery of B DNA
Core - bases
Periphery - sugar phosphate chain
Diameter of A, B and Z DNA and their sugars
A DNA - 23 Å, C3 endo
B DNA - 20 Å C2 endo
Z DNA - 18 Å C2 and C3 endo
Where is the major groove and minor groove formed in B DNA
Major Groove - N7 Purine
Minor - N3 Purine
Helical turn of all the DNA
A DNA - 11
B DNA - 10
Z DNA - 12
Pitch/ axial height and confirmation of all the DNA
A DNA - 24.6 Å, anti
B DNA - 34 Å, anti
Z DNA - 45.6 Å, anti and syn
Major and minor groove of all DNA
A DNA - Major - Narrow and deep,
Minor - Wide and shallow
B DNA - Major - Wide and deep
Minor - Narrow and deep
Z DNA - Major - Flat
Minor - Narrow and deep
Where is A DNA found?
DNA RNA Hybrid
Which sequence is favoured by Z DNA
G and C
How is Z DNA formed from B DNA
Negative supercoiling (topoisomerase), 5 methylated cytosine, high salt conc.
Who described the triple helical nucleic acid
Falsenfeld and Rich
Who described the triple helical nucleic acid
Falsenfeld and Rich
What kind of strand form a triple helix. Name circumstances for forming triple DNA
A dsDNA having homopurine and homopyrimidine sequence strand.
Low pH forms triple stranded DNA
Name the orientation and hoogsteen hydrogen bonding in the case of
A. Pyrimidine rich on homopurine rich strand
B. Purine rich on homopurine rich strand
A. Orientation is parallel and hoogsteen hydrogen bonding
B. Orientation is antiparallel and reverse hoogsteen hydrogen bonding
What is H DNA
When a triple DNA formed that is intramolecular triplex
Building blocks of G Quadruplex
G quartets or G tetrads
G Quadruplex formed by which bond?
Cyclic hoogsteen hydrogen bonding
G Quadruplex stability dependent on?
Monovalent cations, K and Na.
And with coordination of positively charged cations with electronegative O6 atom
What does intramolecular and intermolecular folding requires in G Quadruplex
Intramolecular needs four or more G rich sequences
Intermolecular needs two or four strands that give rise to parallel or antiparallel strands.
What stabilises DNA
Base stacking interaction and hydrogen bond
Factors that affect melting temperature of DNA
Hydrogen bonds, more H bonds more melting point
Presence of Mg and Na, they neutralize the repulsion between phosphate group
