The Red function of phage lambda mediates the alteration of an interspersed repeated DNA sequence from the kangaroo...

The kangaroo rat D. ordii is shown to contain an interspersed repeated sequence 3.25 kb in length. This sequence undergoes alteration (deletions) when cloned into a Red+ lambda vector but is stable in a Red- vector. Using the Red- clone it is shown that deletions are the result of the activity of the lambda Red, or E. coli RecE, recombination systems. Mixed infection experiments demonstrate that this activity is acting in trans. The deletions appear to yield fragments of specific size, suggesting that the recombination system is recognizing a specific sequence. The demonstration of small homologous fragments in the animal genomic DNA suggests that a similar system of recombination may exist in D. ordii.