Propagation of some human DNA sequences in bacteriophage lambda vectors requires mutant Escherichia coli hosts.

Abstract

The growth of clones of human genomic DNA fragments in a bacteriophage .lambda. vector was examined in a number of different E. coli hosts. A large proportion (8.9%) of the phages carrying different fragments of the human genome fail to grow on standard rec+ hosts but will grow on hosts carrying mutations in the recB, recC and sbcB genes. Heteroduplex analysis by EM of DNA from 4 of these phages revealed substantial secondary structure, including snap-back regions 200-500 base pairs in length. Such structures were not found in phages from the same DNA library that grow in rec+ hosts. These results are interpreted in the light of prior observations showing that inverted repetitions cloned in phage .lambda. can be propagated in recB recC sbcB hosts but not in rec+ hosts.