Independent Distribution Law

Mendel, as he continued his experiments, undertook the task of elucidating whether the results previously obtained were similar when crossing plants with a pair of differential characters. He selected plants of pure lines with smooth (AA) and yellow (BB) seeds, which are characters dominant, and plants of pure lines with wrinkled (aa) and green (bb) seeds, which are characters recessive.
In forming the gametes, each parent contributed one allele from each pair: AB and ab. After fertilization, the only combination possibility for individuals of the F1 generation was AaBb, that is, heterozygous and dihybrid genotypes. The manifestation of this genotype in the seeds was that all were similar to the dominant parent: smooth and yellow; therefore, the two recessive characters again disappeared from the phenotype.
He sowed these F1 dihybrid seeds and allowed self-fertilization, resulting in the F2 generation.
When analyzing the phenotype, the seeds obtained in the new generation (F2) realized that indeed, the characters were separated independently one from the other in a constant relationship, thus he obtained: 9 smooth and yellow seeds, 3 smooth and green seeds, 2 rough and yellow seeds, and 1 rough seed and green.

To facilitate the appreciation of these genetic combinations, the Punnett square can be used, placing the genotypes of the gametes on the axes.
male and female and within the table the genotypes of the descendants.
The examples described correspond to the type of quantitative inheritance because the characters are defined and different from each other, which is why they are also called discontinuous characters.
Mendel was very successful in selecting the characters he used in his crosses because the getres for each character is located on different (non-homologous) chromosomes and therefore each pair is inherited independently of one of the other. However, with the studies that Morgan and his group of geneticists did, it is known that independent distribution cannot be made if the pairs of genes that cross exist on the same pair of chromosomes as they are linked, which generally prevents segregation Independent; Sometimes the linkage can break due to crossover and then the genes can be separated.