Difficulty: Easy
Correct Answer: They are short DNA sequences that hybridize only to a specific target base sequence (often distinguishing single-base variants)
Explanation:
Introduction:Not all pathogenic variants create or abolish restriction enzyme sites. Allele-specific oligonucleotide (ASO) probes allow detection of known sequence variants, including single-nucleotide changes, by stringent hybridization. This question clarifies what ASO probes are and how they function in diagnostics.
Given Data / Assumptions:
Concept / Approach:Because ASOs bind only their perfectly complementary sequence under chosen conditions, they enable yes/no detection of a particular allele regardless of nearby restriction sites. This is especially useful when the mutation does not alter an enzyme motif (i.e., is not an RFLP).
Step-by-Step Solution:
1) Design two probes: one perfectly matching the wild type, one matching the mutant.2) Hybridize each probe to DNA immobilized on a membrane or to PCR products under high-stringency conditions.3) Detect probe binding via label (radioactive, fluorescent, or enzymatic) to determine genotype.Verification / Alternative check:ASO-based genotyping is widely used for known point mutations (e.g., specific CFTR variants), with controls verifying stringency and specificity.
Why Other Options Are Wrong:
a) Inserting restriction sites is neither necessary nor typical for diagnostics.b) Functional gene replacement is gene therapy, not allele detection.d) VNTR analysis detects length polymorphisms, not single-base alleles by hybridization.e) Antibodies detect proteins, not DNA alleles.Common Pitfalls:Confusing ASO probes with restriction-based RFLP assays; using low stringency that fails to discriminate single-base differences.
Final Answer:Short oligonucleotides that hybridize specifically to a target allele, enabling single-base variant detection.
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