A DISCREPANCY BETWEEN GENETIC AND PHYSICAL LENGTHS ON THE CHROMOSOME OF BACTERIOPHAGE LAMBDA

Abstract

A genetic map is an arrangement of genes in which the distance between any pair of genes is proportional to the average number of exchanges between them. Such a map will correspond to the actual distribution of genes on a chromosome only if the probability of exchange and recovery of recombinants is uniform along the chromosome. It was the purpose of the present investigation to detect any extensive departure from uniformity in the probability of exchange or recovery along the chromosome of bacteriophage A. It has been shown that recombination in bacteriophage h occurs by breakage and joining of the double-stranded DNA molecule which composes the phage chromosome (MESELSON and WEIGLE 1961 ; KELLENBERGER, ZICHICHI and WEIGLE 1961 ; IHLER and MESELSON 1963; MESELSON 1964). Unexpected features of the results of It was noticed that the distribution of parental DNA among progeny phages of certain genotypes was not as expected from random breakage of the chromosome during recombination. The results reported here elaborate and help to clarify those observations.