Circular genetic map of satellite bacteriophage P4.

A genetic map of satellite bacteriophage P4 has been constructed by means of standard multifactor crosses. The genetic map appears to be a circular permutation of the mature DNA physical map. In addition, a set of markers appear to be linked both to the left and to the right of the same gene alpha. These facts suggest that the P4 genetic map is circular. Since terminal redundancy and/or cyclic permutation are not known to be present in P4 mature DNA, the circularity of P4 genetic map may reflect the physical circularity of the molecules involved in the recombination process. The low frequency of recombination and the strong negative interference observed are in agreement with the above hypothesis.