<P> However, although this process begins at prenatal age, it stops at prophase I. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, called the dictyate . After menarche, these cells then continue to develop, although only a few do so every menstrual cycle . </P> <P> Meiosis I of ootidogenesis begins during embryonic development, but halts in the diplotene stage of prophase I until puberty . The mouse oocyte in the dictyate (prolonged diplotene) stage actively repairs DNA damage, whereas DNA repair is not detectable in the pre-dictyate (leptotene, zygotene and pachytene) stages of meiosis . For those primary oocytes that continue to develop in each menstrual cycle, however, synapsis occurs and tetrads form, enabling chromosomal crossover to occur . As a result of meiosis I, the primary oocyte has now developed into the secondary oocyte and the first polar body . </P> <P> Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II . However, this process is also halted at the metaphase II stage until fertilization, if such should ever occur . When meiosis II has completed, an ootid and another polar body have now been created . </P> <P> Synchronously with ootidogenesis, the ovarian follicle surrounding the ootid has developed from a primordial follicle to a preovulatory one . </P>

In oogenesis what is the end result of the two meiotic divisions