A GENETIC ANALYSIS OF PRIMARY PRODUCTS OF BACTERIOPHAGE LAMBDA RECOMBINATION

[摘要] Primary products of bacteriophage lambda recombination that display heterozygosity as a consequence of the presence of regions of heteroduplex DNA are rare in standard λ crosses. Phage manifesting heterozygosity at a given allele are evident when recombinants, emerging from a cross, are selected for an exchange in a neighboring interval. We show that the abundance of such heterozygotes can be increased 10- to 20-fold by selection on an E. coli indicator that is defective in methyl-directed mismatch repair ( mut L). Thus, the activity of the methyl-directed mismatch repair system is, at least in part, responsible for the low frequency of detectably heterozygous phage emerging from a standard cross. In a mut L indicator, many primary products of recombination are replicated without the intervention of mismatch repair.—The products of a six-factor phage cross have been plated on a mut L indicator allowing visual detection of those phage products heterozygous for one of the allelic pairs, c I. By genetic analysis, we show that the heteroduplex regions of these primary products of recombination are on the average about 4 kb in length and can include as much as half of the lambda genome.

[学科分类] 医学（综合）