Mendel's second law
When two heterozygous individuals of the first generation (F1) are crossed with each other, the recessive traits that did not appear in F1 reappear in F2 in a ratio of 3:1.
In F1 individuals, of the two different alleles for seed color, only one is manifested. When the heterozygous yellow individual (Aa) forms the gametes, the alleles are separated and each gamete only contains one of them.
During gamete production, meiosis occurs, so each gamete contains a unique allele for each gene. With fertilization, variation is ensured. For each trait, an organism inherits two alleles, one from each parent. This means that in somatic cells, one allele comes from the mother and one from the father. These can be homozygous or heterozygous.
That is to say: