21.4 locating genes, genetic screening & counselling

Question 1

what is a dna probe?

Answer 1

short, single stranded pieces of dna that have a label attached & complementary

Question 2

describe the 2 types of dna probes.

Answer 2

1) radioactively labelled probes
- isotope 32P -> identified by x-ray film exposed by radiation
2) fluorescently labelled probes
- bound to target dna sequence & emits light with UV light

Question 3

what is needed to make the dna probe?

Answer 3

sequence of the part of the allele that is being located

Question 4

what is dna hybridisation?

Answer 4

separated dna strands are mixed with the dna probe which binds through complementary base
pairing

Question 5

how are particular alleles identified by using dna probes? (3)

Answer 5

• double stranded dna is heated (denatured) to separate the strands
• dna hybridisation
• binding site is identified by radioactivity / light of dna probe

Question 6

in which 2 ways are genetic screening useful?

Answer 6

1) screening for mutant allele - determine risks of having kids
2) screening for mutated tumour suppressor genes - risk of cancer, determine lifestyle & check-ups

Question 7

give 2 advantages of using identified alleles to make personalised medicine.

Answer 7

1) advise & healthcare based on genotype - decide which drug & does for maximum effectiveness
2) avoid drugs that causes harm / false hope