What is EP and how do you solve zebrafish problems?

Early pressure (EP) is basically stopping chromosomes from segregating to different cells, so the products at the end of meiosisII basically look like the products of meiosis I. It is used to create gynogenetic diploids for half-tetrad analysis, which is used to map genes. The procedure is mock fertilization of oocytes with UV-irradiated (dead) sperm and application of early pressure to block chromatid segregation in the second meiotic division. Removal of EP causes the cells to divide, and the chromatids separate (whether during EP or after I am not sure), so that you end up with diploid cells containing only moms genetic information. Since you start with a heterozygote, no crossover will generate homozygous mutant (q) and homozygous wt (p) progeny (essentially, one chromosome to each daughter cell) and recombination will generate heterozygous progeny (r and s). R.F.=(r+s)/total, but since the homozygous mutant progeny are the only ones you can distinguish (het.=wt too), and there ...  more