In this chapter, we focused on a number of interesting applications of genetic engineering, genomics, and biotechnology. At the same time, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions?

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?

Key Concepts

Allele-Specific Oligonucleotide (ASO) Testing

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.

Homozygous Recessive Genotype

A homozygous recessive genotype occurs when an individual has two identical alleles for a recessive trait, such as the mutation causing sickle-cell anemia. In the case of sickle-cell anemia, the mutation in the HBB gene leads to the production of abnormal hemoglobin. Individuals who are homozygous recessive for this mutation will express the disease phenotype, as they lack a normal allele to compensate for the defective one.

Sickle-Cell Anemia and Its Genetic Basis

Sickle-cell anemia is a genetic disorder caused by a mutation in the beta-globin gene, 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.