Determination of the amount of homology required for recombination in bacteriophage T4.

Homology is an important feature of recombination. We have used the rll cistrons of bacteriophage T4 to determine the extent of homology required for recombination. We varied the amount of homologous DNA available for recombination in both marker rescue experiments and deletion-by-deletion crosses. Our results suggest that the primary pathway for recombination in T4 requires 50 bp of homology. Our finding that recombination is detectable when fewer than 50 bp of homology are available suggests that there is a second, less efficient pathway of recombination in T4. This pathway may be used during the formation of deletions.