nucleic acid structure Flashcards
nucleoside
sugar + base
nucleotide
sugar + base + phosphate
where are new nucleotides added
3’ OH group
key difference between RNA and DNA
DNA only has a hydroxyl (OH) group at the 3’ carbon, while RNA has a hydroxyl at the 3’ AND the 2’
difference between uracil and thymine
thymine has a CH3 group at (if think) the 2’ carbon where uracil only has an H
what is required for the polymerization of DNA/RNA
requires an enzyme DNA or RNA polymerase
requires a form of energy - ATP, CTP, GTP, TTP
why are triphosphates high in energy
binding of 3 phosphates is unfavourable, w/ 3 negative ions in close proximity, removing the outermost releases energy which can be used to like nucleotide monomers to the polymer (nucleic acid)
number of hydrogen bonds between A and T
2
number of hydrogen bonds between C and G
3
DNA primary level of structure
single strand of dna - nucleotide sequence - phosphodiester bonds
DNA secondary level of structure
DNA double helix - hydrogen bonds
DNA tertiary structure
helix winds to form chromatin/chromosomes
purine bases
adenine and guanine, bigger
pyrimidine bases
thymine and cytosine, smaller
why is watson-crick base pairing good?
correct geometry - same distance between bases in the strands
allows for base stacking to improve stability
no bulging and bases are close enough to for nc interactions
2 things that hold dna helix together
H bonds between base pairs
stacking interactions
stacking interactions
bases are essentially hydrophobic
ID-ID and ID-PD interactions occur between to help stabilize
what does water have to do with DNA helix formation
hydrophobic effect!!! bc base pairs are pretty much hydrophobic
benefit of major and minor grooves
regions where proteins bind to DNA
