**Question:** The following methods can be used to detect the point mutation in the beta ((3)-globin gene that causes sickle cell anemia, except:

A. Polymerase Chain Reaction (PCR)
B. Sanger sequencing
C. Real-time PCR
D. Electrophoresis

**Core Concept:**

Sickle cell anemia is a genetic disorder caused by a point mutation in the beta-globin gene, specifically a single nucleotide substitution from adenine to guanine at nucleotide position 6 (HbS). Diagnostic methods aim to detect this mutation and its consequences. The following methods are valid:

**Why the Correct Answer is Right:**

Methods like PCR, Sanger sequencing, and real-time PCR are used to amplify, sequence, and quantify the DNA containing the beta-globin gene, respectively. These techniques help detect the point mutation directly from the patient's blood sample or leukocytes.

**Why Each Wrong Option is Incorrect:**

Electrophoresis is a technique that separates DNA fragments based on their size and charge, allowing for the visualization of amplified DNA products. However, it does not directly detect the point mutation but rather the presence of the amplified gene fragments.

**Clinical Pearl / High-Yield Fact:**

PCR-based methods, such as Sanger sequencing, are gold standard techniques for detecting genetic mutations like sickle cell anemia. However, electrophoresis is often used as a complementary method to analyze the amplified fragments obtained from these mutation detection techniques.

**Correct Answer:**

**Correct Answer: D. Electrophoresis**

In the context of detecting the point mutation in beta-globin gene, electrophoresis is incorrect because it only detects amplified DNA fragments and does not directly identify the specific mutation causing sickle cell anemia. PCR-based methods like Sanger sequencing or real-time PCR are more appropriate for mutation detection.