How did Rudolf Virchow contribute to the cell theory? I know that he added the third tenet "Omnis cellula e cellula", which means that all cells come from [pre-existing] cells, but HOW did he come to this conclusion?

Choose the best definition of allele. a. one of several possible versions of a gene, which each produce a different phenotype b. an organism that's purebred for a given trait c. the process of fertilizing a plant with pollen from another plant d. a set of genes that are located on the same chromosome and so are tightly linked