gene probes Flashcards
What is a gene probe?
Single stranded; Piece of DNA; Complementary to a known base sequence in a specific allele of a gene;
Explain why labelled (radioactive/fluorescent) DNA probes are used to locate specific DNA fragments.
DNA is invisible on medium used; so the label allows detection;
Explain why gene probes are usually many bases long, rather than just the mutated base code.
Single base or short base sequence occurs many times; Sequence of many bases unlikely to occur elsewhere;
Gene probes are usually complimentary to an exon in DNA of a faulty protein, not an intron. Explain why
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;
How is DNA hybridisation used to locate specific alleles of genes?
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.
What can labelled gene probes be used to screen patients for?
Heritable conditions; responses to drugs; health risks;
What is genetic counselling?
Using the results of DNA probe analysis to advise families on the likelihood of genetic conditions occurring in their children.
What is personalised medicine?
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.
