En transposition from the A1 locus on chromosome 3

--Etienne Kaszas and Peter A. Peterson

This is an extension and amplification of the Nowick and Peterson study (1981). In this study, 190 germinal derivatives from the autonomous allele a-m(papu)--see cross below--were isolated to study the transposition of En from its initial site at the A1 locus. The transposition of En at the new location was confirmed by crosses of the stable colorless or pale derivatives to responsive tester lines (a-m(r) and a-m1). Our study, although based only on 190 derivatives, is in agreement with Nowick and Peterson's data (MGG 183:440-448, 1981): 24% of the derivatives do contain a linked En, as it appears in the table of percentages below. Around 10% of the lines do contain an independent En. The other classes indicate either an En loss, or a changed En that gave incomplete signals, or two or more Ens.
 
Study* no En En indep. En linked Two or more Ens Low freq. of En
1 28 12 29 21 10
2 16 9 24 25 26
*1, Nowick and Peterson, 1981: 1627 derivatives analyzed

2, This study, 1988 and 1989: 190 derivatives analyzed

Cross: a-m(papu)/a sh2 x a sh2; progeny expected are 1/2 spotted round and 1/2 colorless shrunken; exceptions are colorless round or pale round.

An estimate of A1 - En distance was calculated (direction undetermined), as shown in the figure. This distribution is not random. 60% of the values are in the range of 5 to 20 map units. These results are supportive of Nowick and Peterson (1981), where En transposed preferentially between 5 and 15 map units from A1. Tests for precise location of En are underway.

Figure.


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