Consider the following pedigree.

Predict the mode of inheritance of the trait of interest and the most probable genotype of each individual. Assume that the alleles A and a control the expression.

Verified step by step guidance

1. Step 1: Analyze the pattern of affected individuals across generations. Notice that both males and females are affected, and the trait appears in every generation, suggesting it is likely a dominant trait.
2. Step 2: Check if the trait skips generations. Since affected individuals are present in each generation, this supports the idea of a dominant mode of inheritance rather than recessive.
3. Step 3: Consider the genotypes of the parents in generation I. Since individual I-2 is affected and I-1 is unaffected, and they have both affected and unaffected children, I-2 is likely heterozygous (A/a) and I-1 is homozygous recessive (a/a).
4. Step 4: Assign genotypes to individuals in generation II based on their parents' genotypes and their affected status. For example, affected individuals are likely A/a, and unaffected individuals are a/a.
5. Step 5: Continue this logic for generations III and IV, using the inheritance pattern and the genotypes of parents to predict the most probable genotype of each individual, remembering that affected individuals must have at least one dominant allele (A).

Key Concepts

Pedigree Analysis

Pedigree analysis is a tool used to study the inheritance patterns of traits through generations in a family. It uses standardized symbols to represent individuals and their traits, helping to identify dominant, recessive, autosomal, or sex-linked inheritance. Understanding how traits appear and skip generations is key to predicting genotypes.

Modes of Inheritance

Modes of inheritance describe how genetic traits are transmitted from parents to offspring. Common modes include autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. Recognizing patterns such as affected individuals in every generation or skipping generations helps determine the mode.

Genotype Prediction Using Alleles

Genotype prediction involves determining the genetic makeup (e.g., AA, Aa, or aa) of individuals based on their phenotype and family history. Using dominant (A) and recessive (a) alleles, one can infer carriers and affected individuals by analyzing who expresses the trait and how it segregates in the pedigree.