Question

question 12
in the pedigree above, circles represent females, squares represent males, and shaded figures represent individuals expressing a specific trait. the expression of this trait is most likely due to which of the following?
autosomal recessive inheritance
a codominant relationship of a single pair of alleles
autosomal dominant inheritance
sex - linked recessive inheritance

Explanation:

1. Autosomal Recessive: Requires carriers (unshaded) to have affected (shaded) children, but here many shaded individuals have shaded parents, which is less likely for recessive (usually skips generations, affected from carriers).
2. Codominance: Shows both traits, but pedigree shows a single trait (shaded/unshaded), not codominant expression.
3. Autosomal Dominant: Affected individuals (shaded) have at least one affected parent (e.g., shaded parents have shaded children, and even when one parent is shaded, some children are shaded). Dominant traits don’t skip generations, which matches the pedigree (affected individuals in multiple generations, no skipping).
4. Sex - linked Recessive: Affects more males, but here females are also shaded (e.g., shaded females with shaded male partners, and shaded female children), inconsistent with X - linked recessive (males more affected, females need two recessive alleles or affected father + carrier mother).

Answer:

C. Autosomal dominant inheritance