TANDEM DUPLICATIONS OF THE <i>r</i>II REGION OF BACTERIOPHAGE T4D

Abstract

Abstract Genetic analyses of ten duplication strains of bacteriophage T4D isolated from an rJ101 × rl589 cross reveal that all ten duplications segregate structurally normal chromosomes (r segregants); six of the duplications have been shown to segregate inviable particles, presumed triplications, with the same frequency that they yield r segregants; viable triplication segregants have been isolated from four of the duplications; the rII region from the r1589 parent maps to the left of that from the rJ101 parent in nine of the duplications, while the tenth exhibits the reverse order. These observations are consistent with the hypothesis that the duplications are tandem duplications of a portion of the genome which includes the rII region. The evidence for triplications segregated from the duplications is not readily compatible with stabilized terminal redundancies as the basis of the duplications. Evidence is presented that the length of the duplication is compensated by a deletion of non-essential information elsewhere in the phage genome.