It has been known for some time that when insect cells are infected with two different strains of baculovirus at the same time, new variant viruses with slightly different specificities can form after the two starting viruses have replicated. These new viruses are the product of homologous recombination between the two starting viruses. Detailed analysis of this phenomenon revealed that a region of DNA that is only 79 base pairs (bp) long and located within the p143 helicase gene was sufficient to permit homologous recombination between different baculoviruses. More importantly, this 79-bp DNA segment may be responsible for the host ranges of different baculoviruses. Therefore, alteration of some of the nucleotides within this 79-bp DNA segment may allow researchers to generate baculoviruses with modified (expanded) insect specificities.