gebe probes

Question 1

1. What is a gene probe?

Answer 1

Single stranded; Piece of DNA; Complementary to a known base sequence in a specific allele of a gene;

Question 2

2. Explain why labelled (radioactive/fluorescent) DNA probes are used to locate specific DNA fragments.

Answer 2

DNA is invisible on medium used; so the label allows detection;

Question 3

3. Explain why gene probes are usually many bases long, rather than just the mutated base code.

Answer 3

Single base or short base sequence occurs many times; Sequence of many bases unlikely to occur elsewhere;

Question 4

4. Gene probes are usually complimentary to an exon
   in DNA of a faulty protein, not an intron. Explain why.

Answer 4

Introns not in mRNA so not expressed in polypeptide; Mutations of these exons affect amino acid sequences that produce the faulty protein; So important to know if exons affected, rather than any other part of DNA;

Question 5

5. How is DNA hybridisation used to locate specific alleles of genes?

Answer 5

Double stranded DNA is heated to separate the two strands. A DNA probe is added, complimentary to the specific allele of a target gene. The mixture is cooled so the DNA probe recombines (anneals) with the complimentary sequence of DNA. Dominant and recessive alleles of a gene will have slightly different sequences, so specific probes can be used to see if the individual is homozygous or heterozygous.

Question 6

6. What can labelled gene probes be used to screen patients for?

Answer 6

Heritable conditions; responses to drugs; health risks;

Question 7

7. What is genetic counselling?

Answer 7

Using the results of DNA probe analysis to advise families on the likelihood of genetic conditions occurring in their children.

Question 8

8. What is personalised medicine

Answer 8

Using the results of DNA probe analysis to advise individuals based on their own genotype. Some peoples genes may mean a particular drug is more or less effective on them than others.