Question

Which of the following is a recessive genetic disorder?

• A. Huntington's disease
• B. Sickle cell anemia
• C. Achondroplasia
• D. Marfan syndrome

Hint:

If a question lists common genetic diseases, remember that Sickle Cell, Cystic Fibrosis, and Phenylketonuria (PKU) are classic examples of autosomal recessive inheritance.

Answer 1

The Correct Option is B

To solve the question, "Which of the following is a recessive genetic disorder?" let's analyze each option provided:

1. Huntington's disease: This is a genetic disorder caused by a dominant allele. It results in the progressive breakdown of nerve cells in the brain. Since the disorder is dominant, an individual only needs one copy of the mutant allele to be affected. Therefore, this is not a recessive disorder.
2. Sickle cell anemia: This is a recessive genetic disorder caused by a mutation in the hemoglobin-beta gene found on chromosome 11. An individual must inherit two copies of the mutated allele (one from each parent) to manifest the disease. This confirms that sickle cell anemia is indeed a recessive disorder.
3. Achondroplasia: This disorder is caused by a mutation in the FGFR3 gene and is inherited in an autosomal dominant manner. Individuals with one copy of the mutated gene will display achondroplasia characteristics. Hence, it is not a recessive disorder.
4. Marfan syndrome: This is also a dominant genetic disorder caused by mutations in the FBN1 gene. Individuals with one defective allele will have the disorder. Thus, it is not a recessive disorder.

Based on the information provided, Sickle cell anemia is the only recessive genetic disorder among the options given.

Thus, the correct answer is Sickle cell anemia.

Answer 2

Step 1: Understanding the Concept:
Genetic disorders are classified as dominant or recessive based on whether one or two copies of the mutated gene are required for the disease to manifest.
Step 2: Detailed Explanation:
- Sickle cell anemia is an autosomal recessive disorder. This means an individual must inherit two copies of the mutated hemoglobin gene (HbS) to have the disease. Carriers (HbAS) usually do not show symptoms.
- Huntington's disease (Option A) is an autosomal dominant neurodegenerative disorder.
- Achondroplasia (Option C), a common form of dwarfism, is an autosomal dominant condition.
- Marfan syndrome (Option D), which affects connective tissue, is also an autosomal dominant disorder.
Step 3: Final Answer:
Sickle cell anemia is the recessive disorder among the choices provided.