Complex sentence: After post-doctoral training in the United States of America at the UCLA School of Medicine and the National Cancer Institute (NCI), he joined the NCI, with which he was associated till 1984 as the chief of the molecular genetics section.
Split into simpler sentences: After post-doctoral training in the United States of America at the UCLA School of Medicine and the National Cancer Institute (NCI). He joined the National Cancer Institute after his post-graduation, with which he was associated till 1984 as the chief of the molecular genetics section.