DNA probes detect complementary sequences

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DNA probes detect complementary sequences

A DNA probe is a labelled sequence designed to pair with a complementary target under suitable conditions. Hybridisation can help detect a particular allele or sequence. Interpretation depends on probe specificity, experimental controls and the reliability of the test.

Genetic information can inform some diagnoses or drug-response predictions, but a result may be uncertain or only change a probability. Counselling can help people understand implications for themselves and relatives. Privacy, informed consent and the limits of prediction matter alongside the detection method.

Sequence direction matters: a probe written 5′–ACGT–3′ pairs with 3′–TGCA–5′. Writing the target in its own 5′-to-3′ direction reverses its order. A detected variant may have incomplete penetrance or interact with other variants and the environment. Separate the reliability of detecting a sequence from the strength of a prediction about its consequences.

Worked example: A short probe is 5′–ACGT–3′. Write its antiparallel complementary target.

Pair A with T and C with G.

Keep the strands antiparallel.

Answer: 3′–TGCA–5′.

Check your understanding: Does a detected risk-associated allele prove that a person will develop a condition?

Answer: No.

Why: Penetrance, environment and other variants can affect risk; a detection result is not necessarily a certain prediction.