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adenine
adenosine
guanine
guanosine
thymine
thymidine
cytosine
cytidine
uracil
uridine
“-sine”
purines
“-ine”
pyrimidines
adenine structure
guanine structure
thymine structure
cytosine structure
uracil structure
nucleotide
monomer with a structure including a sugar, nitrogenous base, and phosphate
nucleoside
a nitrogenous base with a ribose sugar
purines have…
two rings
pyrimidines have…
1 ring
N-glycosidic bond is between…
nitrogen and sugar
hydrogen bonds are between…
nucleotides
purines have how many hydrogen bonds?
2
pyrimidines have how many hydrogen bonds?
3
phosphodiester bonds are between…
phosphate and ribose
what are some identifying traits of B-form DNA?
2 antiparallel strands linked by phosphodiester bonds, twists to the right, each turn is about 10 base pairs, major and minor groove, bases are interior and sugars are exterior which exposes the sides of bases to the solvent for DNA binding proteins
how is bacterial DNA compacted in a cell?
the plasmid DNA is circular - it is wound up and supercoiled, they are slightly underwound so they coil up on themselves
topoisomerase
an enzyme that cuts one or both strands of supercoiled DNA, alters the structure, then reconnects broken strands
topoisomerase 1
cuts 1 strand of DNA
topoisomerase 2
cuts 2 strands of DNA
what are the differences between DNA and RNA?
RNA is a single-stranded polynucleotide, it is less stable than DNA, it can break itself down (the extra OH can Nu- attack its phosphoryl group)
the higher the G-C content…
the higher the melting temperature
the stability of DNA helix
base sacking interactions - bases stack on top of each other and maximize vanderwhal interactions (pi-pi bonds)
ionic interactions - catins (Mg2+) stabilize DNA helix (with negative phosphate group)
number of hydrogen bonds - G-C form 3, A-T form 2
how can DNA be denatured?
at high heat (melting) which separates the two strands
how can DNA be reannealed?
by cooling below the Tm (half-way point) about 20-25C
