bio 4D Flashcards
Gel electrophoresis
what is gel electrophoresis
a technique used to separate DNA fragments based on their molecular size
components of gel electrophoresis
well: indent in the gel that DNA is loaded into
standard ladder: mixture of DNA fragments of known length that are used to infer the size of the fragments
agarose gel: sponge-like gel that contains pores for the DNA fragments to move through (smaller DNA fragments are able to move through all the pores whilst the large ones are stuck behind)
buffer solution: ion-rich solution that carries electrical current through the agarose gel
ethidium bromide: fluorescent dye that binds to the DNA fragments and allows for it to be visualised under a UV light
how does gel electrophoresis work
DNA is negatively charged (due to the sugar-phosphate backbone) so in order for the fragments to cross the agarose gel, an electrical current is passed through the gel using two electrodes (positive is at the end) and the DNA fragments move towards the end of the gel (opposites attract). smaller fragments move faster and further so after a few hours, the current is turned off and the fragments stop moving and settles into bands
what are factors that affect the rate of DNA movement
velocity: the higher the voltage, the faster the DNA fragments will move
gel composition: the lesser the density and agarose composition, the easier it is for DNA to travel through
buffer concentration: the greater the concentration of ions in the buffer, the more electrical current is conducted through the gel, meaning the DNA moves faster
time: the longer the gel is left, the more likely that all the DNA fragments pass through to the positively charged electrode
