wild-type   crossed   with  black,
   vestigial-winged  flies  produce  heterozygous  F[1] dihybrids, all of
   which appear wild-type.
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   A  testcross  of  F[1]  females  with  black,  vestigial-winged  males
   produced 2,300 F[2] offspring.
<P>
<lI> If   the  2  genes  were  on  different  chromosomes,  independent
assortment should yield equal numbers of the 4 types of F[2].
<lI> If   the  2  genes  were  on  the  same  chromosome,  each  allele
combination  (B^+  vg^+  and  b  vg) should stay together and only
yield parental phenotypes in the F[2].
<lI> The  high percentage of parental phenotypes in the F[2], with some
non-parental  (recombinant)  phenotypes  imply  the  2  genes  are
physically close to each other on the same chromosome.
<P>
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