Answer:
The most appropriate answer would be the discovery of the gene.
In 1909, term "gene" was coined by Wilhelm Johannsen who described gene as the physical and functional units of heredity.
Genes are the protein-coding segment of the DNA which are present on the chromosome.
The increasing information about the functioning and segregation of genes and chromosomes lead to the rediscovery of the Mendel laws.
Genes are the hereditary units which were considered as factors by Mendel.