After the demonstration of gene dosage effect for indophenol oxidose A
(IPO-A) , i.e. CuZn superoxide dismutase (CuZn-SOD or SOD-1)  in trisomy
21, we localized the gene of CuZn-SOD on the segment including the distal part
of 21q21 and 21q22.1 .
In order to analyse this dosage effect in trisomy 21 by D/G or G/G
translocation (centromeric fusion), we measured the red blood cells SOD
activity in the following cases of unbalanced translocation . The method we
used is described by LavelIe et al .
Compared to seventy cases of free trisomy 21 already studied in our
laboratory, the gene dosage effect is, as expected, identical in both types of
These results are in disagreement with the data published by Kedziora et
al.  who claimed that IPO-A and SOD-1 activities were not increased in cases
of trisomy 21 resulting from a tronslocation D/G or G/G.
We concluded that there is no detectable chromosome position effect on
the CuZn-SOD gene activity in trisomy 21 by centromeric D/G or G/G
translocation. The gene dosage effect for this enzyme is identical in free
trisomy 21 and in trisomy 21 by translocation .
CuZn activity in erythrocytes of trisomics 21 by
|Case||Age (years)||Sex||SOD (g/g Hb)
|Trisomics 21 by tronslocation (n = 6) 1672 ±
|Trisomics 21 with free trisomy (n = 70) 1645 ±
|Controls (n = 67) 1107 ± 87*
|(* mean ± SD)
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