BRAINCAKELocating Specific Alleles with Probes
Labelled DNA probes and DNA hybridisation can be used to find out whether a person carries a particular allele, such as a mutated allele that causes a genetic disorder.
1. The base sequence of the allele is found by DNA sequencing.
2. A single strand of DNA complementary to part of the allele is made, and many copies are produced using PCR.
3. A fluorescent or radioactive label is attached, making the DNA probe.
4. DNA is extracted from the person's cells (for example from blood), cut into fragments with restriction endonucleases and heated to separate the strands.
5. The probe is added and the mixture cooled. If the allele is present, the probe hybridises with it.
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Key terms in this lesson
- heterozygous
- Having two different alleles of a particular gene.
- gel electrophoresis
- A technique that separates DNA fragments (or other charged molecules) by size, by passing an electric current through a gel so that smaller fragments move further towards the anode.
- restriction endonuclease
- An enzyme that cuts DNA at a specific base sequence (recognition site), used to cut out genes or produce DNA fragments for genetic engineering or profiling.
- polymerase chain reaction
- A technique for rapidly amplifying small amounts of DNA in vitro, using repeated cycles of denaturation, primer annealing and extension by a heat-stable DNA polymerase.
More in Genetic Engineering and Biotechnology
- Patenting
- GM animals
- Gene Therapy
- DNA Probes
- DNA Hybridisation
- Genetic Screening
- Genetic Counselling
- Personalised Medicine
All 23 lessons in Genetic Engineering and Biotechnology · All AQA A-level Biology topics