In beans, the yellow color of the beans is the dominant feature, the green one is recessive.

In beans, the yellow color of the beans is the dominant feature, the green one is recessive. From crossing plants with yellow beans, the offspring obtained, 3/4 of which are yellow beans, and 1/4 are green. Determine the genotypes of the plants to be bred.

Yellow color is a dominant feature (A). Therefore, phenotypically yellow peas can have the AA or Aa genotype.
Green coloration is a recessive trait (a), therefore green peas always have the aa genotype.
According to Mendel’s third law, when two heterozygous individuals are crossed, the distribution of the genotype of the offspring is 3: 1. According to the condition of the problem, two yellow individuals were crossed, and their descendants were distributed in a ratio of 3: 1. Therefore, both of these individuals could only be heterozygotes: phenotypically yellow with the Aa genotype.