Question

Match the LIST-I with LIST-II 

Choose the correct answer from the options given below: 
 

• A. A-I, B-II, C-III, D-IV
• B. A-IV, B-I, C-II, D-III
• C. A-III, B-II, C-I, D-IV
• D. A-II, B-IV, C-I, D-III

Hint:

Associate keywords: Sickle cell $\leftrightarrow$ Malaria resistance (heterozygous advantage). Huntington's $\leftrightarrow$ Variable age of onset (penetrance/expressivity). PKU $\leftrightarrow$ Multiple symptoms from one gene (pleiotropy). Thalassemia Major $\leftrightarrow$ Severe/fatal homozygous state (lethal effect).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question requires matching specific genetic diseases with the genetic principles or processes they exemplify.
Step 2: Detailed Explanation:
- A. Sickle Cell Anemia: The sickle cell allele in its heterozygous state (one normal allele, one sickle allele) provides resistance to malaria. This is the classic textbook example of heterozygous advantage. So, A matches with II.
- B. Beta Thalassemia (Major): This is the homozygous condition for the beta thalassemia allele, leading to severe anemia and often death before adulthood if left untreated. An allele that causes death when homozygous is known as a recessive lethal allele. This is a lethal gene effect. So, B matches with IV.
- C. Huntington's Chorea: This is an autosomal dominant disorder. Individuals with the allele will develop the disease, but the age of onset and the severity of symptoms can vary greatly. This variation in the expression of a genotype is a hallmark of variable penetrance and expressivity. So, C matches with I.
- D. Phenylketonuria (PKU): A single gene mutation in the PAH gene causes a wide range of symptoms, including intellectual disability, seizures, eczema, and reduced skin and hair pigmentation. When one gene influences multiple, seemingly unrelated phenotypic traits, it is known as a pleiotropic effect. So, D matches with III.
Step 3: Final Answer:
Based on the matching: A $\rightarrow$ II, B $\rightarrow$ IV, C $\rightarrow$ I, D $\rightarrow$ III. This corresponds to option (D).