How is Mendel's law of independent assortment tested experimentally?

Mendel's law of independent assortment is tested experimentally through dihybrid crosses in pea plants.

In more detail, Gregor Mendel, the father of modern genetics, tested his law of independent assortment by conducting dihybrid crosses. A dihybrid cross is a breeding experiment that tracks the inheritance of two traits at once. Mendel chose to study two traits in pea plants: seed colour (yellow or green) and seed shape (round or wrinkled).

Mendel started his experiment by cross-breeding purebred plants that had yellow, round seeds with plants that had green, wrinkled seeds. The first generation (F1) of offspring all had yellow, round seeds, showing that these traits were dominant. He then allowed the F1 generation to self-fertilise, producing a second generation (F2).

In the F2 generation, Mendel observed a 9:3:3:1 ratio of the four possible combinations of traits: yellow-round, yellow-wrinkled, green-round, and green-wrinkled. This ratio was consistent across multiple experiments, providing strong evidence for the law of independent assortment.

The law of independent assortment states that the alleles for different traits segregate, or assort, independently of one another during the formation of gametes. This means that the allele a plant inherits for seed colour does not influence the allele it inherits for seed shape.

Mendel's experiments were groundbreaking at the time and laid the foundation for our modern understanding of genetics. However, it's important to note that the law of independent assortment only holds true for genes located on different chromosomes or far apart on the same chromosome. Genes located close together on the same chromosome tend to be inherited together, a phenomenon known as genetic linkage.

In summary, Mendel's law of independent assortment was tested through careful and methodical breeding experiments in pea plants. These experiments involved tracking the inheritance of two traits across generations and observing the ratios of different trait combinations in the offspring.