Final answer:
Thomas Hunt Morgan's experiments with fruit flies led to the discovery of non-Mendelian genetic ratios, which indicated the presence of genetic linkage and recombination. This contrasted with Mendel's earlier findings of predictable dominant and recessive trait ratios.
Step-by-step explanation:
The discovery of non-Mendelian ratios by Thomas Hunt Morgan came through experiments with fruit flies (Drosophila melanogaster). Morgan observed inheritance patterns that did not match the 3:1 Mendelian ratio expected from Gregor Mendel's pea plant experiments. Mendel's work, which exemplified the laws of inheritance, involved calculating the probability of genetic traits being passed on using large numbers of crosses. Mendel concluded that dominant and recessive traits were inherited at predictable ratios, which was confirmed in his reciprocal cross experiments regardless of which parent contributed which trait.
Morgan's studies conducted in 1911 revealed exceptions to these predictable ratios, indicating a more complex mechanism of inheritance. It was through Morgan's breeding experiments with fruit flies that he discovered genetic linkage and recombination, which occur when genes are located close together on the same chromosome. These linked genes tend to be inherited together, altering the expected Mendelian ratios and leading to a greater understanding of chromosomal theory of inheritance.