gene probes

Question 1

what are DNA probes?

Answer 1

short strands of DNA that have a specific base sequence that’s complementary to the target allele so the probe will bind (hybridise) to the target allele if it is present in a sample. They have labels attached eg radioactive label or fluorescent label so they can be detected

Question 1

why are DNA probes useful?

Answer 1

used to locate specific alleles of genes or to see if a persons DNA contains a mutated allele

Question 2

how do they work?

Answer 2

1. sample of DNA is digested into fragments using restriction enzymes and are separated using electrophoresis
2. they are then transferred to a nylon membrane and incubated with fluorescently labelled DNA probe
3. if allele is present, DNA probe will hybridise (bind)
4. membrane is exposed to UV light and if the gene is present there will be a fluorescent band

Question 3

DNA microarray

Answer 3

screens lots of genes at the same time
1. A DNA microarray is a glass slides with microscopic spots of different DNA probes attached in rows
2. a sample of fluorescent DNA is washed over the array
3. if sample contains any sequences that match any probes, it will stick
4. the array is washed to remove any unbound DNA
5. array is placed under UV light and any labelled DNA attached to a probe will fluoresce