Work

After Renato Dulbecco discovered that tumor viruses operate by incorporating their DNA into the DNA of host cells, David Baltimore and Howard Temin –independently of one another–discovered that viruses with genomes consisting of RNA can also be inserted into host cells' DNA. This takes place through an enzyme known as reverse transcriptase. The discovery that the information in RNA can be transferred to DNA meant that the generally accepted rule that genetic information was only transferred in one direction–from DNA to RNA, to protein–had to be modified.