The antimorphic lds[Hor-D] mutation causes dominant loss of paternally inherited chromosomes in early embryonic mitoses. Experimentally, the "Horka" mutation is useful for inducing X chromosome loss to generate gynandromorphs.
This method was described in Szabad et al. (1995).
Janos Szabad's tips for maximizing the recovery of gynandromorphs
Gynandromorphs are more common when mwh[1] lds[Hor-D] e[1]/TM3, Sb[1] Ser[1] males from stock 42293 are crossed to y[1] v[1] f[1] mal[F1] virgin females from stock 180 than in crosses to females of other genotypes. Gynandromorphs comprise ~20% of the progeny of y[1] v[1] f[1] mal[F1] females and 1-2% of progeny of other females. The genetic basis of this strain difference is not known. Gynandromorphs eclose with a 2-3 day delay. For best results, cultures should not be overcrowded.
There are two predominate classes of male progeny: y[1] v[1] f[1] mal[F1]/Y male progeny from regular Y-bearing sperm and y[1] v[1] f[1] mal[F1]/0 male progeny from nullo-Y sperm produced by the high rate of nondisjunction in lds[Hor-D] males. Both have creamy orange eyes from the combination of v and mal mutations. Other progeny appear to be males with red eye color, but they are actually cryptogynandromorphs. Although their eyes are v[-] in genotype, the presence of heterozygous v[+]/v[-] diplo-X tissue in their bodies leads to red eyes from vermilion nonautonomy.
Some progeny of lds[Hor-D] males have both normal bristles and short, thin bristles as shown below. They are diplo-4//haplo-4 mosaics resulting from loss of the paternal fourth chromosome. The short, thin bristles result from loss of one copy of the haploinsufficient Minute gene RpS3A.
To generate gynandromorphs with one red and one white eye and with half y[-] pigmentation as shown below, mate homozygous y[-] w[-] females to lds[Hor-D]/TM3, Sb[1] Ser[1] males. Other interesting markers for distinguishing female from male tissue include sn[-] and f[-] mutations and X-linked transgenes expressing marker proteins.
It is often desirable to examine the external phenotypes of gynandromorphs (and other flies) in flattened cuticle preparations. A convenient method is described in Szabad (1978).
A note on making gynandromorphs using a ring-X chromosome
Historically, gynandromorphs have been generated most often using a ring-X chromosome called R(1)2, In(1)w[vC]. Ring-X stocks must be selected continually for mitotic instability to be experimentally useful in recovering gynandromorphs. R(1)2, In(1)w[vC] stocks in the Bloomington collection have not been maintained under selection and they have stabilized. It is not clear if they could be destabilized by selection.
