Lecture 3- Intro to nucleic acids Flashcards
Central dogma of molecular biology
DNA–RNA–Protein
Nucleotide components
Sugar, one to three phosphates, and a base
Major difference between DNA and RNA
DNA lacks a 2’ hydroxyl group on the sugar and there for is not succeptible to base attack
Nucleoside components
Sugar and a base
Sugar in RNA
Ribose, five member ring sugar
Sugar in DNA
Deoxyribose
Does not have a 2’ hydroxyl group
Phosphodiester linkages
Form between the 5’ hydroxyl and 3’ hydroxyl groups on the sugars
5’ to 3’ directionality
Pyrimidine bases
C,T, and U
Flat planar 6-member ring with two nitrogens
Purine bases
A and G
Flat planar 6 member ring fused to a 5 member ring with two nitrogens in each
Structure of R handed B- DNA
Antiparallel strands
Complementary base pairing (A to T, G to C)
AT bonds have 2 h bonds
GC bonds have 3 h bonds
One turn of the helix is 10.5 BP (34 A or 3.4 nm)
Major and minor grooves formed
A-DNA
Right handed
Shorter than B-DNA and likely appears in dehydrated samples of DNA, DNA-RNA hybrid, or dsDNA
Z-DNA
Left handed
Structure that repeats every 2 base pairs
Not favorable
High salt and some cations can induce Z-DNA
Hoogsteen base pairing
Purine bases can flip their normal conformation and form a new set of H bonds
Impact of Ionic strength on Tm
High salt stabilizes dsDNA therefore increasing the Tm
Impact of pH on Tm
Inversely proportional to Tm
High concentrations of OH denature DNA by forming H bonds with bases
