How does a positive ASO test for sickle-cell anemia determine that an individual is homozygous recessive for the mutation that causes sickle-cell anemia?

ASO testing is a molecular technique used to detect specific mutations in DNA. It involves using short, labeled DNA probes that are complementary to the target mutation. If the target mutation is present in the individual's DNA, the probe will bind to it, indicating a positive result. This method is particularly useful for identifying homozygous recessive genotypes, as it can confirm the presence of two copies of the mutated allele.

A homozygous recessive genotype refers to having two identical alleles for a particular gene, both of which are recessive. In the case of sickle-cell anemia, the mutation in the HBB gene leads to the production of abnormal hemoglobin. An individual must inherit two copies of the mutated allele (one from each parent) to express the disease phenotype, which is confirmed through ASO testing when both alleles are detected.

Sickle-cell anemia is a genetic disorder caused by a mutation in the HBB gene on chromosome 11, leading to the production of sickle-shaped red blood cells. This condition is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene to exhibit symptoms. Understanding the genetic basis of sickle-cell anemia is crucial for interpreting ASO test results and determining an individual's genotype.