Final answer:
The genotypes for individuals with the autosomal recessive disorder alkaptonuria can be determined from a pedigree. Individual 1 is aa, while individuals 2 and 3 are AA. A test cross is used to determine if a dominant expressing individual is heterozygous or homozygous for the trait.
Step-by-step explanation:
Determining Genotypes in a Pedigree
In genetics, predicting the genotypes of individuals within a pedigree involves understanding inheritance patterns. The question pertains to an autosomal recessive trait, which in this case is represented by alkaptonuria. Individuals with alkaptonuria are indicated in blue within a pedigree chart and carry the genotype aa. Those who are unaffected display either genotype AA (homozygous dominant) or Aa (heterozygous). The given information includes the genotypes of three individuals within such pedigree. According to the data provided:
- The genotype of individual 1 is aa
- The genotype of individual 2 is AA
- The genotype of individual 3 is AA
A test cross can be utilized to discern between homozygous dominant and heterozygous genotypes by crossing with a homozygous recessive individual and analyzing the offspring. This process allows determination of whether the dominant expressing parent is heterozygous or homozygous for the dominant trait.
In terms of Mendelian genetics, knowing the parents' genotypes can help predict potential offspring genotypes. For example, if neither parent has an autosomal recessive disorder but their offspring does, it can be inferred that both parents must carry at least one recessive allele and are thus heterozygous. If an individual is unaffected by the disorder and their genotype is unknown, it is represented with an 'A?', indicating they have at least one normal (dominant) allele.