Stages Parasexual cycle

1 stages

1.1 diploidization
1.2 mitotic chiasma formation
1.3 haploidization

stages
diploidization

occasionally, 2 haploid nuclei fuse form diploid nucleus—with 2 homologous copies of each chromosome. mechanism largely unknown, , seems relatively rare event, once diploid nucleus has been formed can stable , divide form further diploid nuclei, along normal haploid nuclei. heterokaryon consists of mixture of 2 original haploid nuclear types diploid fusion nuclei.

mitotic chiasma formation

chiasma formation common in meiosis, 2 homologous chromosomes break , rejoin, leading chromosomes hybrids of parental types. can occur during mitosis @ lower frequency because chromosomes not pair in regular arrangement. nevertheless, result same when occur—the recombination of genes.

haploidization

occasionally, nondisjunction of chromosomes occurs during division of diploid nucleus, 1 of daughter nuclei has 1 chromosome many (2n+1) , other has 1 chromosome few (2n–1). such nuclei incomplete multiples of haploid number termed aneuploid, not have chromosome number sets such n or 2n. tend unstable , lose further chromosomes during subsequent mitotic divisions, until 2n+1 , 2n-1 nuclei progressively revert n. consistent this, in e. nidulans (where normally, n=8) nuclei have been found 17 (2n+1), 16 (2n), 15 (2n–1), 12, 11, 10, , 9 chromosomes.

each of these events relatively rare, , not constitute regular cycle sexual cycle. outcome similar. once diploid nucleus has formed fusion of 2 haploid nuclei different parents, parental genes can potentially recombine. and, chromosomes lost aneuploid nucleus during reversion euploid mixture of in parental strain.