The accompanying pedigree shows the transmission of albinism (absence of skin pigment) in a human family.

Using allelic symbols of your choice, identify the genotypes of the male and his two mates in generation I. 

Verified step by step guidance

1. Examine the pedigree to determine the inheritance pattern of albinism. Albinism is typically inherited in an autosomal recessive manner, meaning individuals must inherit two recessive alleles to express the trait.
2. Choose allelic symbols to represent the trait. For example, use 'A' for the dominant allele (normal pigmentation) and 'a' for the recessive allele (albinism).
3. Identify the genotype of the male in generation I. If he has offspring with albinism, he must carry at least one recessive allele ('a'). If he does not express albinism himself, his genotype is heterozygous ('Aa').
4. Determine the genotype of the first mate in generation I. If their offspring express albinism, the mate must also carry at least one recessive allele ('a'). If the mate does not express albinism, their genotype is likely heterozygous ('Aa').
5. Analyze the genotype of the second mate in generation I. Follow the same logic as above, considering whether their offspring express albinism and whether the mate expresses the trait themselves. If offspring express albinism, the mate must carry at least one recessive allele ('a').

Key Concepts

Pedigree Analysis

Pedigree analysis is a diagrammatic method used to trace the inheritance patterns of traits through generations in a family. It helps identify how traits, such as albinism, are passed down, revealing whether they are dominant or recessive. Understanding the symbols and structure of a pedigree is crucial for determining genotypes based on observed phenotypes.

Genotype vs. Phenotype

The genotype refers to the genetic makeup of an individual, while the phenotype is the observable expression of that genotype, influenced by environmental factors. In the context of albinism, individuals with the genotype 'aa' exhibit the phenotype of albinism, whereas those with 'AA' or 'Aa' do not. Distinguishing between these concepts is essential for accurately identifying genotypes in a pedigree.

Dominant and Recessive Alleles

Alleles are different forms of a gene that can exist at a specific locus on a chromosome. In the case of albinism, if the trait is recessive, it requires two copies of the recessive allele (e.g., 'a') for the phenotype to be expressed. Conversely, a dominant allele (e.g., 'A') can mask the presence of a recessive allele, making it vital to understand these relationships when determining genotypes from a pedigree.