4. In the 1947 News Letter I mentioned a complex translocation involving chromosomes 3 and 5 in which a break had occurred in 5L midway between the knob and the end, while the centromere of 3 had been fractured. The distal portion of 5L had become translocated to 3S. The linkage relations of genes in chromosome 3 have been determined with respect to the point of translocation, which is the centromere in this case. Due to the fact that directed segregation of the chain of 3 (in strains with two normal chromosomes 5, one normal 3 and the interchanged 3's) may occur with certain modifiers present, it was not feasible to use pollen abortion as the marker for the translocation, and root-tip counts were resorted to. Plants with 20 chromosomes had the intact chromosome 3 while those with 21 chromosomes had 3S and 3L as separate entities. The following data were obtained:

Lg2-A	36	% recombination
C-Lg2	36.5	"	(C represents the centromere)
C-Rg	14.8	"
Lg2-Rg	16.0	"
C-A	50	"

Anderson and Randolph state that the centromere lies between d₁ and

ts₄. The data obtained in the study of this translocation permit a more definite location and show that the centromere lies between d₁ and Rg, with Rg lying between ts₄ and the centromere. The linkage map is shown below (C standing for the centromere):

cr d C Rg ts₄ ba na A et ga₇

0 18 25 40 47 .64 75 103 115 121

M. M. Rhoades