BRAINCAKEDNA Probes
A DNA probe is a short length of single-stranded DNA with a base sequence that is complementary to part of a target gene or allele. Because of complementary base pairing, the probe binds only to DNA that contains that sequence.
A probe is labelled so that it can be located once it has bound:
• a radioactive label (often phosphorus-32), detected by exposing the sample to X-ray film, a technique called autoradiography
• a fluorescent label, which glows under ultraviolet (UV) light.
To make a probe, scientists must first know the base sequence of the target, for example the sequence of a disease-causing allele. A single strand with the complementary sequence is made, many copies are produced using PCR, and the label is attached.
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Key terms in this lesson
- allele
- One of two or more alternative versions of a gene, occupying the same locus on homologous chromosomes.
- 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.
- dna hybridisation
- The binding of a single strand of DNA, or RNA, to another strand with a complementary base sequence, forming a double-stranded hybrid.
More in Genetic Engineering and Biotechnology
- GM plants
- Patenting
- GM animals
- Gene Therapy
- DNA Hybridisation
- Locating Specific Alleles with Probes
- Genetic Screening
- Genetic Counselling
All 23 lessons in Genetic Engineering and Biotechnology · All AQA A-level Biology topics