TAICHUNG, TAIWAN
National Chung Hsing University Cytological 10L breakpoint of B-10L translocations --Cheng, Y-M, Lin, B-Y Pachytene structure of ten heterozygous B-10L translocations was determined. Three chromosomes (10, 10-B, and B-10) are expected to pair in a T-configuration, and the point where three arms meet is the location of the breakpoint (for details see the separate article of this issue). The break-position is represented by the ratio of the length between the centromere and the breakpoint to that of 10L. Each value is the average of at least three cells. The result conforms to the previously published data on linkage of this region (Lin, MNL 48: 182-184, 1974) with the exception of TB-10L9 and TB-10L12. The linkage data place the two translocations proximal to TB-10L16, but the cytological data place them distal to TB-10L11. Also, the order of the two breakpoints is reversed in the two maps. This discrepancy may be due partly to small sample sizes of the linkage analysis.

Table 1. Cytological breakpoint of ten B-10L translocations
 
Translocations Breakpoint on 10L Average Lin�s dataa
TB-10L19 0.07, 0.04, 0.07, 0.06 0.06 1.30
TB-10L20 0.08, 0.08, 0.10 0.09 0.98
TB-10L22 0.12, 0.12, 0.09, 0.06, 0.11 0.10 0.98
TB-10L1 0.23, 0.24, 0.20 0.22 0.80
TB-10L16 0.25, 0.34, 0.28 0.29 0.40
TB-10L11 0.29, 0.27, 0.29, 0.37 0.31 0.33
TB-10L12 0.60, 0.40, 0.47 0.49 0.41
TB-10L9 0.55, 0.45, 0.56 0.52 0.61
TB-10L6 0.53, 0.60, 0.58, 0.59 0.58 0.32
TB-10L21 0.72, 0.77, 0.68, 0.69, 0.73 0.72 0.30
arecombination ratio of breakpoint-R/ g-R (from Lin, 1974)
 
 

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