Unit 1: DNA gels, blots and probes

Question 1

what is gel electrophoresis?

Answer 1

way of separating different fragment lengths of DNA

Question 2

describe gel electrophoresis process?

Answer 2

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

Question 3

what is denaturing and annealing?

Answer 3

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

Question 4

why is the denaturing temperature higher for G:C complementary base pairs?

Answer 4

because they have more hydrogen bonds than A:T

Question 5

through genetic mapping, what pieces of information can be obtained?

Answer 5

locate genes on chromosomes
establish order of genes
establish approx distance between genes

Question 6

what are genetic markers?

Answer 6

genes that can be easily identified and located

Question 7

what is a single locus probe?

Answer 7

have a complementary sequence at only one location within the genome being probed

Question 8

what are single probes used for?

Answer 8

paternity tests for to screen fro mutations

Question 9

what are multi locus probes?

Answer 9

have a complementary sequence that occurs at many locations of the genome being probed

Question 10

what are multi locus probes used for?

Answer 10

DNA profiles and fingerprints

Question 11

what are DNA microarrays?

Answer 11

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

Question 12

how is DNA detected in the wells during microarrays?

Answer 12

using fluorescence

Question 13

what is the difference between a probe and a primer?

Answer 13

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

Question 14

why is DNA blotting necessary?

Answer 14

electrophoresis gels shrink and deformm and so are unsuitable materials for further processing or storing DNA

Question 15

what is DNA blotting

Answer 15

when DNA fragments are drawn out of the gel onto a intracellular or nylon filter