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.) Two normal parents have five children, four normal and one albino.

Key Concepts

Recessive Traits

Recessive traits are characteristics that only manifest when an individual has two copies of the recessive allele. In the case of albinism, the trait is caused by a recessive allele, meaning that an individual must inherit this allele from both parents to express the condition. If an individual has one dominant allele, the dominant trait will be expressed instead.

Genotype vs. Phenotype

Genotype refers to the genetic makeup of an individual, specifically the alleles they carry, while phenotype is the observable expression of those genes. For example, a person with one dominant and one recessive allele for albinism (genotype Aa) will have a normal phenotype, whereas a person with two recessive alleles (aa) will exhibit albinism. Understanding this distinction is crucial for determining the possible genotypes of parents and offspring.

Punnett Squares

Punnett squares are a tool used in genetics to predict the possible genotypes of offspring from a cross between two parents. By mapping out the alleles contributed by each parent, one can visualize the probability of different genotypes in the offspring. In this scenario, using a Punnett square can help determine the genotypes of the normal parents and their albino child, clarifying the inheritance pattern of the recessive trait.