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Howard M. Temin was one of David Baltimore's Nobel co-recipients. Both scientists were awarded the 1975 Nobel Prize in Physiology or Medicine for their groundbreaking research on the reverse transcriptase enzyme, which is crucial for the replication of retroviruses like HIV. Temin's work focused on the discovery of reverse transcriptase in Rous sarcoma virus, while Baltimore's research demonstrated its presence in other retroviruses.