Final answer:
Lederberg and Tatum showed that bacterial conjugation is a process by which genes are directly transferred between bacteria using a conjugation pilus. By disrupting the process at various times, they identified the sequential transfer of genes, demonstrating how conjugation contributes to bacterial genetic recombination.
Step-by-step explanation:
Lederberg and Tatum demonstrated that conjugation occurs in bacteria through a series of experiments where they mechanically disrupted the conjugation process at different time intervals. They observed that recipient cells could acquire functional genes from donor cells, such as the wild-type A gene in cases where the recipient had a mutant version. These experiments showed that genes could be transferred sequentially, depending on the length of conjugation, allowing them to deduce the gene order on the bacterial chromosome.
Their work provided evidence for direct cell-to-cell transfer of genetic material in bacteria, which was important for understanding bacterial genetic recombination and mapping the bacterial chromosome.
These results also suggested that bacterial DNA transfer occurs through a mechanism that is distinct from the transformation process described by Griffith, where external DNA is absorbed from the environment.