Final answer:
To determine whether the genotype is AaBb or AABb, you can use a test cross with a homozygous recessive genotype. If all offspring show the dominant phenotype, the genotype is homozygous for that trait. If any offspring show the recessive phenotype, the genotype is heterozygous for that trait.
Step-by-step explanation:
In order to determine whether the genotype is AaBb or AABb, we can use a test cross. A test cross is performed by crossing the genotype in question with a homozygous recessive genotype. Out of the five genotypes given, only the aabb genotype is homozygous recessive. So, to determine if the original genotype is AaBb or AABb, we would perform a test cross with the aabb genotype.
When performing the test cross, we would cross the original genotype with the homozygous recessive genotype. If any of the offspring show the recessive phenotype, then the original genotype must be heterozygous for that trait. If all of the offspring show the dominant phenotype, then the original genotype must be homozygous for that trait.
For example, if we perform a test cross between AaBb and aabb, and all of the offspring show the dominant phenotype, then the original genotype is AABb. If any of the offspring show the recessive phenotype, then the original genotype is AaBb.