Unit 1: DNA gels, blots and probes Flashcards
what is gel electrophoresis?
way of separating different fragment lengths of DNA
describe gel electrophoresis process?
DNA sample is placed in a well in a gel immersed in a buffer solution
DNA is negatively charged so moves towards the positive electrode
DNA fragment is separated along their lane according to size.
shorter fragments move faster and further through gel.
one lane would have a ladder of known lengths of DNA for reference
what is denaturing and annealing?
hydrogen bonds can be heated at approx 95°C to break them. this denature DNA resulting in single strands of DNA
when temperature is lowered, complementary single strands remake double helix - annealing
why is the denaturing temperature higher for G:C complementary base pairs?
because they have more hydrogen bonds than A:T
through genetic mapping, what pieces of information can be obtained?
locate genes on chromosomes
establish order of genes
establish approx distance between genes
what are genetic markers?
genes that can be easily identified and located
what is a single locus probe?
have a complementary sequence at only one location within the genome being probed
what are single probes used for?
paternity tests for to screen fro mutations
what are multi locus probes?
have a complementary sequence that occurs at many locations of the genome being probed
what are multi locus probes used for?
DNA profiles and fingerprints
what are DNA microarrays?
thousands of different probes are attached individually into a series of micro wells - allows a sample of DNA to be tested by many different probes at the same time
how is DNA detected in the wells during microarrays?
using fluorescence
what is the difference between a probe and a primer?
both are short single stranded complementary sequences of DNA. probes are used so that we can identify location of a specific sequence whereas primers are used so that DNA polymerase can locate a start point for DNA replication
why is DNA blotting necessary?
electrophoresis gels shrink and deformm and so are unsuitable materials for further processing or storing DNA
what is DNA blotting
when DNA fragments are drawn out of the gel onto a intracellular or nylon filter
