Gce Model Questions Vol1 2023 Biology Question 10

The pedigree below represents a three‑generation family affected by an autosomal recessive metabolic disorder that results in accumulation of substrate X. Squares denote males, circles females; filled symbols indicate affected individuals, half‑filled symbols indicate carriers, and unfilled symbols are unaffected non‑carriers. The proband is a 5‑year‑old boy (III‑2) who is affected. His parents (II‑1 and II‑2) are phenotypically normal. His maternal grandfather (I‑2) is affected, while his paternal grandparents are unaffected. [Pedigree description] : I‑1 (male, unaffected) — I‑2 (female, affected) → II‑2 (female, carrier)\nI‑3 (male, unaffected) — I‑4 (female, unaffected) → II‑1 (male, carrier)\nII‑1 × II‑2 → III‑1 (female, unaffected), III‑2 (male, affected), III‑3 (female, carrier).