Biochemical properties of DNA Flashcards
describe oswald Avery
mixed virulent and non virulent bacteria strains and injected into mouse
mouse only lived when the DNA was destroyed - otherwise, it got into the non virulent strain and killed the moust
describe DNA solubility
soluble in water and low salt - due to polyanionic PO43-
not soluble in ethanol
forms salt with Na and Mg at neutral pH
describe DNA viscosity
viscous as phosphate groups attract water.
viscosity decreases when H bonds are broken/bases exposed
describe UV absorption
optimal at 260nm wavelength
bases are what absorbs UV, so higher for ss than double stranded
how does UV absorption indicate concentration
make known standard of absorbance vs concentration and then find out unknown absorbance
how can denaturing be caused
pH changes or increased temp
effect of denaturing on UV absorption and viscosity
increases UV absorption
decreases viscosity
x and y axis of DNA melting curve -
x axis = temp
y axis = optical density (absorption)
–> as temp increases, optical density increases
describe Tm
temp at which 50% of DNA is melted
factors affecting Tm
size of molecule
ph/ionic strength
GC content (higher due to 3 bonds)
what affects steepness of transition
how homogenous it is - more so, narrow range
why do AT bubbles form
becuase they have a lower mp, so are more likely to be split there than GC
describe hybridisation
DNA of 2 different species are denatured and mixed
-can renature or hybridise
describe probes as an application of hybridisation
labelled
designed to be complementary to DNA of interest, helps us locate it
describe agarose gel
polysaccharide from seaweed
larger pores
