Question

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the genotypes of the parents and offspring. (When two alternative genotypes are possible, list both.)
Construct a pedigree of the families in (b) and (c). Assume that one of the normal children in (b) and one of the albino children in (c) become the parents of eight children. Add these children to the pedigree, predicting their phenotypes (normal or albino).

Accepted Answer

Understand the inheritance pattern: Albinism is a simple recessive trait, meaning that an individual must inherit two recessive alleles (aa) to express the albino phenotype. A heterozygous individual (Aa) will have a normal phenotype but can pass on the recessive allele. Determine the genotypes of the parents and offspring: Analyze the family data provided in the problem. Use the phenotypes of the parents and offspring to deduce their genotypes. For example, if two normal parents have an albino child, both parents must be heterozygous (Aa). Construct the pedigree for families (b) and (c): Use standard pedigree symbols (squares for males, circles for females, shaded for albino, unshaded for normal) to represent the family members. Label each individual with their genotype if it can be determined or list possible genotypes if ambiguous. Predict the phenotypes of the eight children: If one normal child from family (b) (likely genotype Aa) and one albino child from family (c) (genotype aa) become parents, use a Punnett square to determine the probability of their offspring being normal (Aa or aa) or albino (aa). Add the predicted children to the pedigree: Extend the pedigree to include the eight children, marking their phenotypes (normal or albino) based on the probabilities calculated in the Punnett square. Ensure the pedigree remains clear and follows standard conventions.

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Concetti chiave

Recessive Inheritance

Genotype vs. Phenotype

Pedigree Analysis