Mendel noticed that different traits did not travel together. The law of independent assortment states that alleles of different genes segregate independently of one another during gamete formation. The allele a gamete receives for one gene does not influence the allele it receives for another gene.

The physical basis is the random orientation of different chromosome pairs at metaphase I of meiosis. Genes located on different chromosomes therefore assort independently. Genes that are close together on the same chromosome are genetically linked and deviate from independent assortment.

The law predicts the classic 9:3:3:1 ratio in dihybrid crosses. Linkage mapping and recombination frequencies quantify how often genes assort independently. Modern genetics still relies on this principle when analyzing the inheritance of multiple traits or loci.

• Alleles of different genes assort independently
• Occurs during meiosis
• True for genes on different chromosomes
• Produces 9:3:3:1 ratios in dihybrid crosses