The Linkage Disturbance Involved in the Chromosome Translocation I. Of Drosophila, and Its Probable Significance

The chromosomal abnormality in Drosophila, known as translocation I., is located at approximately 76.9 on the third chromosome. 2. The presence of translocation does not affect the crossover values for the first 45 units in the left-hand end of the chromosome. To the right of this point, the per cent. of crossing over progressively decreases as the locus of translocation is approached, reaching its minimum of less than one third normal value in the region between ebony and rough. 3. The same results are obtained no matter whether the translocation is homozygous or heterozygous. 4. The fact that the results are the same in both heterozygous and homozygous flies shows that the attached fragment is not interpolated in the third chromosome, but is attached to its side. The resulting chromosome is thus of a type which has hitherto not been reported: that is, one in which the genes are not in a single linear series.