Step 1: Understanding the Problem:
A pedigree chart shows the inheritance of a particular trait across generations. Analyzing the pattern of affected vs. unaffected individuals helps deduce the trait's mode of inheritance. Step 2: Approach and Formula:
Use standard pedigree analysis rules:
- If unaffected parents have affected offspring $\rightarrow$ the trait is strictly Recessive.
- Check for gender bias to determine Autosomal vs. Sex-linked. Step 3: Detailed Explanation:
- Looking at the visual chart: In the first generation, both parents (square for male, circle for female) are unaffected (white/unshaded).
- However, they produce an affected daughter (shaded circle) and an affected son (shaded square) in the second generation.
- This specific pattern—where the disease "skips a generation" and unaffected carriers produce an affected child—is the absolute hallmark of a recessive trait. (If it were dominant, at least one parent must have been affected).
- Furthermore, because an unaffected father passes the disease to his daughter, it cannot be an X-linked recessive trait. (In X-linked recessive, an affected daughter must inherit an affected X from a completely affected father).
- Therefore, the trait must be inherited via an autosome. Step 4: Final Answer:
The pedigree represents an Autosomal recessive trait.
