Question

Analyse the following pedigree and write the (i) Pattern of inheritance. (ii) Give one example of disease showing such an inheritance pattern.

Hint:

Cheat Sheet:
1. Unaffected parents $\rightarrow$ Affected child = Recessive.
2. Affected parents $\rightarrow$ Unaffected child = Dominant.
3. Horizontal distribution (both sexes affected equally) = Autosomal.

Answer 1

Step 1: Understanding the Concept:
To determine the pattern, we look for key indicators like skipping generations or the phenotype of parents compared to offspring.
Step 2: Detailed Explanation:
1. Analysis of the pedigree:
- In the first generation, both parents are unaffected (normal).
- They produce an affected male child in the second generation.
- This "skipping of a generation" where normal parents produce an affected child is a hallmark of a recessive trait.
- Since an affected male is produced from normal parents, and subsequently an affected female is seen from an affected father and normal mother (indicating the mother was likely a carrier), it follows the Autosomal Recessive pattern.
2. Example: Diseases like Sickle cell anemia, Cystic fibrosis, and Phenylketonuria follow this autosomal recessive pattern.
Step 3: Final Answer:
Pattern: Autosomal Recessive. Example: Sickle cell anemia.