As discussed here, chromosomes carrying RanGAP[Sd] cause haploid nuclei acquiring chromosomes carrying Rsp[s] to remain decondensed during spermatogenesis and, consequently, for the RanGAP[Sd]-bearing chromosomes to be inherited preferentially. The strength of this Segregation Distorter effect depends on the presence of gain-of-function mutations in the M(SD), E(SD) and St(SD) genes.
By moving SD components from their usual second chromosome positions to the X or Y chromosomes, one can generate males that produce predominantly X- or Y-bearing sperm.
Males producing mostly X-bearing sperm
Dp(2;Y)cb25-4 is a Y chromosome into which a segment of the second chromosome carrying Rsp[s] has been inserted. In the presence of RanGAP[Sd], spermatids inheriting this Y chromosome are less likely to produce functional sperm.
The following stock may be used to generate males producing mostly X-bearing sperm, but it requires some explanation.
The strength of the SD effect depends heavily on the relative number of copies of Rsp[s] and E(SD)[1]. In order to see strong elimination of Dp(2;Y)cb25-4 and strongly female-biased broods, males carrying Dp(2;Y)cb25-4 must be homozygous for RanGap[Sd], Rsp[i] and E(SD)[1]. Males from this stock may be crossed to females from one of the SD stocks below.
The Dp(2;Y)cb25-4, Rsp[s]/+; RanGAP[Sd] Rsp[i] E(SD)[1]/CyO male progeny (which will have relatively weak SD effects) should then be crossed to females from one of the SD stocks to produce Dp(2;Y)cb25-4, Rsp[s]/+; RanGAP[Sd] Rsp[i] E(SD)[1]/RanGAP[Sd] Rsp[i] E(SD)[1] males, where the SD effect should be strong.
Any two SD second chromosomes can be combined to to maximize the sex bias. We have not tested combinations to know which produce the strongest female bias in progeny broods.
Males producing mostly Y-bearing sperm
If you followed the description above for generating males that produce predominantly X-bearing sperm, you'll see immediately that an X chromosome carrying Rsp[s] can be used to generate males producing predominantly Y-bearing sperm. In fact, the same stocks can be used.
C(1;YL)19-3 is a Y chromosome in which the short arm (YS) has been replaced by X euchromatin and a large segment of X centric heterochromatin. A section of second chromosome centric heterochromatin including Rsp[s] is inserted in YL. In crosses, C(1;YL)19-3 segregates like a regular X chromosome.
Males carrying C(1;YL)19-3 with RanGAP[Sd] and two copies of E(SD)[1] will produce mostly Y-bearing sperm. These males can be produced in a variety of ways using stock 64332 as the source of C(1;YL)19-3, stocks 64322, 64323 and 64324 (and perhaps other stocks) as sources of RanGAP[Sd] Rsp[i] E(SD)[1] chromosomes and other stocks as sources of relevant balancers. The SD effect should be strong in the resulting C(1;YL)19-3, y[1] w[1], Rsp[s]/Y; RanGAP[Sd] Rsp[i] E(SD)[1]/RanGAP[Sd] Rsp[i] E(SD)[1] males. Again, combinations of RanGAP[Sd] Rsp[i] E(SD)[1] chromosomes from stocks 64322, 64323 and 64324 (and perhaps other stocks) could be tested for maximal bias.
