Rick, C. M.
The following data indicate four new trisomic identifications of tester genes, including two hitherto unidentified linkage groups. All progenies were F2 from trisomic F1's with one dose of the recessive marker.
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Family Chromosome Gene 2N 2N+l Total
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58L268 4 e+ 90 20 110
e 11 0 11
58L269 4 e+ 148
seedling e 24
58L267 6 yv^+ 77 3 80
yv 11 0 11
58L294 6 yv^+ 83 16 99
yv 11 1 12
58L294 6 yv^+ 292
seedling 31
58L290 9 ah^+ 67 13 80
ah 11 0 11
58L290 9 ah^+ 268
seedling ah 21
57L78-80 11 cm^+ 209 32 282
cm 73 4 36
58L285 11 cm^+ 130
seedling cm 29
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The segregation for e definitely places this linkage group on chromosome 4.
Tests with normal segregations for e have been completed with all other
trisomics except triplo-3.The trisomic segregation of yv for chromosome 6 was anticipated since Gilbert had discovered the linkage between yv and Mi. The appearance of a single triple recessive individual suggests that yv probably lies at a considerable distance from the centromere. Tests have been completed between yv and all other trisomies except triplo-2 and -3 with normal segregations.
The trisomic segregation of ah in triplo-9 could have been predicted because ah is linked with wd and the latter had been identified with this chromosome by earlier trisomic tests.
Segregation for cm even under our best conditions for phenotypic expression, has presented difficulties. Expression in cm is so variable that some individuals can be distinguished from cm/cm only by progeny test. The data for triplo-11 seem convincing, considering that many other families tested at the same time gave normal F2 segregations. The proportion of cm trisomics is disturbingly high and cannot be explained away as misclassification of heterozygotes since all 4 cm trisomics yielded only cm progeny.