Pedigree Analysis

Pedigree analysis traces a trait across generations to deduce its inheritance pattern from the distribution of affected individuals. An autosomal dominant trait typically appears in every generation without skipping, because even a single dominant allele is enough to express the phenotype, and affected individuals usually have at least one affected parent. Because the gene lies on an autosome, males and females are affected in roughly equal numbers. Autosomal recessive inheritance is unlikely here since recessive traits often skip generations, appearing only when two carriers mate. X-linked recessive inheritance would show a male-biased pattern, with more affected males than females and characteristic transmission through carrier mothers, contradicting the equal-sex observation. Y-linked inheritance is ruled out because such traits pass only from father to son and never affect females, yet the pedigree affects both sexes. As outlined in NCERT Class 12, Chapter 5 (Principles of Inheritance and Variation), pedigree symbols and patterns help distinguish dominant from recessive and autosomal from sex-linked traits. As a logical check, continuous vertical transmission with equal sex involvement uniquely fits the autosomal dominant pattern, confirming the answer.