ISOGAMY. “There are numerous species which are sexual and do not have this problem because they do not produce males or females. Yeast, for example, are isogamous sexual organisms which have two mating types which fuse and recombine their haploid genomes. Both sexes reproduce during the haploid and diploid stages of their life cycle and have a 100% chance of passing their genes into their offspring.”
https://en.m.wikipedia.org/wiki/Evolution_of_sexual_reproduction#Two-fold_cost_of_sex