21.4 locating genes, genetic screening and counselling

Question 1

what is a probe?

Answer 1

short, single- stranded length of DNA that has some sort of label attached that makes it easily identifiable

Question 2

what are the 2 most commonly used probes?

Answer 2

• radioactive

- fluorescent

Question 3

how are probes used to identify particular alleles of genes?

Answer 3

1. DNA is made single- stranded by heat
2. DNA is mixed with probes
3. site at which probe binds can be identified by radioactivity or fluorescence

Question 4

what is DNA hybridisation?

Answer 4

single stranded DNA that has a probe attached to it

Question 5

how do we locate specific alleles of genes?

Answer 5

1. DNA fragment is produced that is complementary to allele we are trying to locate
2. PCR is used to produce multiple copies
3. marker is attached to this DNA fragment to make a DNA probe
4. DNA from the person is made single- stranded by heat
5. probes added to DNA
6. DNA is washed to remove any unattached probes
7. if fluoresces or radioactive then person has allele