1157:
133:
copies of each chromosome. The mechanism is largely unknown, and it seems to be a relatively rare event, but once a diploid nucleus has been formed it can be very stable and divide to form further diploid nuclei, along with the normal haploid nuclei. Thus the heterokaryon consists of a mixture of the
145:
formation is common in meiosis, where two homologous chromosomes break and rejoin, leading to chromosomes that are hybrids of the parental types. It can also occur during mitosis but at a much lower frequency because the chromosomes do not pair in a regular arrangement. Nevertheless, the result will
285:
Parasexuality has become a useful tool for industrial mycologists to produce strains with desired combinations of properties. Its significance in nature is largely unknown and will depend on the frequency of heterokaryosis, determined by cytoplasmic incompatibility barriers and it is also useful in
100:
The parasexual cycle resembles sexual reproduction. In both cases, unlike hyphae (or modifications thereof) may fuse (plasmogamy) and their nuclei will occupy the same cell. The unlike nuclei fuse (karyogamy) to form a diploid (zygote) nucleus. In contrast to the sexual cycle, recombination in the
174:
Each of these events is relatively rare, and they do not constitute a regular cycle like the sexual cycle. But the outcome would be similar. Once a diploid nucleus has formed by fusion of two haploid nuclei from different parents, the parental genes can potentially recombine. And, the chromosomes
724:
Butler G, Rasmussen MD, Lin MF, Santos MA, Sakthikumar S, Munro CA, et al. (June 2009). “Evolution of pathogenicity and sexual reproduction in eight
Candida genomes”. Nature. 459 (7247): 657–662. Bibcode:2009Natur.459..657B. doi:10.1038/nature08064. PMC 2834264.
162:
of chromosomes occurs during division of a diploid nucleus, so that one of the daughter nuclei has one chromosome too many (2n+1) and the other has one chromosome too few (2n–1). Such nuclei with incomplete multiples of the haploid number are termed
167:, as they do not have even chromosome number sets such as n or 2n. They tend to be unstable and to lose further chromosomes during subsequent mitotic divisions, until the 2n+1 and 2n-1 nuclei progressively revert to n. Consistent with this, in
544:
Hocart MJ, Lucas JA, and
Peberdy JF. "Parasexual recombination between W and R pathotypes of Pseudocercosporella herpotrichoides through protoplast fusion." Mycological Research. 1993 August;97(8):977-983.
116:. This is also true for fungi where the sexual phase is present, although in this case, additional and significant variation is incorporated through the sexual reproduction.
105:
followed by haploidization (but without meiosis). The recombined haploid nuclei appear among vegetative cells, which differ genetically from those of the parent mycelium.
703:
Bennett RJ and
Johnson AD. "Completion of a parasexual cycle in Candida albicans by induced chromosome loss in tetraploid strains." EMBO J. 2003 May 15;22(10):2505-15.
712:
Seervai RNH, Knox SKJ, Hirakawa MK, Porman AM, and
Bennett RJ. "Parasexuality and Ploidy Change in Candida tropicalis." Eukaryotic Cell. 2013 Dec; 12(12): 1629–1640.
185:
219:
626:
Higgins VJ, Miao V, Hollands J (1987). "The use of benomyl and cycloheximide resistance markers in studies of race development by the leaf mold pathogen
183:
The potential to undergo a parasexual cycle under laboratory conditions has been demonstrated in many species of filamentous fungi, including
108:
Both heterokaryosis and the parasexual cycle are very important for those fungi that have no sexual reproduction. Those cycles provide for
89:; while haploidization probably involves mitotic nondisjunctions which randomly reassort the chromosomes and result in the production of
657:
Arnaru J, Oliver RP (1993). "Inheritance and alteration of transformed DNA during an induced parasexual cycle in the imperfect fungus
380:
Durand N, Reymond P, Fevre M (1992). "Transmission and modification of transformation markers during an induced parasexual cycle in
1078:
862:
778:
93:
and haploid cells. Like a sexual cycle, parasexuality gives the species the opportunity to recombine the genome and produce new
175:
that are lost from an aneuploid nucleus during its reversion to a euploid could be a mixture of those in the parental strain.
277:
it is with reduced machinery, or different machinery, and also that unrecognized meiotic cycles may exist in many species.
213:
747:
333:
1133:
948:
256:
171:(where normally, n=8) nuclei have been found with 17 (2n+1), 16 (2n), 15 (2n–1), 12, 11, 10, and 9 chromosomes.
1056:
1113:
1128:
928:
911:
69:). Fusion of the unlike nuclei in the cell of the heterokaryon results in formation of a diploid nucleus (
1191:
1186:
857:
852:
847:
842:
771:
477:
O'Garro LW, Clarkson JM (1992). "Variation for pathogenicity on tomato among parasexual recombinants of
1066:
906:
97:
in their offspring. Unlike a sexual cycle, the process lacks coordination and is exclusively mitotic.
896:
587:"Evidence of parasexual exchange of DNA in the rice blast fungus challenges its exclusive clonality"
837:
78:
28:
1118:
65:) during which nuclei and other cytoplasmic components occupy the same cell (heterokaryosis and
1034:
1029:
825:
820:
764:
207:
191:
1138:
349:
Sidhu GS. (1983). "Sexual and parasexual variability in soil fungi with special reference to
266:
147:
130:
113:
74:
1073:
201:
45:
8:
970:
938:
231:
1083:
1061:
1046:
686:
494:
454:
433:
401:
243:
225:
142:
39:
or the development of sexual structures. It was first described by
Italian geneticist
1181:
1088:
874:
803:
743:
678:
608:
459:
329:
109:
690:
405:
1041:
670:
639:
598:
567:
525:
490:
449:
393:
362:
260:
237:
40:
1123:
1105:
1051:
995:
603:
586:
269:-formation pathway, but retention of a minor pathway. It was suggested that if
879:
159:
82:
643:
530:
509:
1175:
1093:
1024:
990:
901:
867:
1160:
1012:
889:
884:
830:
612:
463:
265:
species concluded that there were recent losses in components of the major
682:
366:
196:
129:
Occasionally, two haploid nuclei fuse to form a diploid nucleus—with two
62:
674:
397:
90:
86:
66:
54:
585:
Zeigler RS, Scott RP, Leung H, Bordeos AA, Kumar J, Nelson RJ (1997).
1000:
975:
965:
953:
134:
two original haploid nuclear types as well as diploid fusion nuclei.
70:
16:
Nonsexual mechanism for transferring genetic material without meiosis
1017:
918:
571:
94:
73:), which is believed to be unstable and can produce segregants by
985:
958:
274:
102:
36:
1007:
980:
813:
85:. Mitotic crossing-over can lead to the exchange of genes on
58:
24:
808:
787:
737:
584:
328:. Cambridge, MA: Blackwell Publishers. pp. 167–68.
756:
554:
Garber ED, Ruddat M (1992). "The parasexual cycle in
57:). A parasexual cycle is initiated by the fusion of
625:
476:
379:
1173:
431:
772:
738:Alexopoulos CJ, Mims CW, Blackwell M (1996).
720:
718:
656:
553:
319:
317:
315:
313:
311:
137:
619:
578:
434:"The mechanism of heterokaryotic growth in
425:
112:variation in the vegetative phase of their
779:
765:
715:
547:
507:
35:for transferring genetic material without
650:
602:
529:
501:
470:
453:
373:
348:
323:
308:
742:. John Wiley and Sons. pp. 196–97.
342:
560:International Journal of Plant Sciences
1174:
53:when referring to its sexual form, or
760:
101:parasexual cycle takes place during
875:Heterogametic sex / Homogametic sex
632:Canadian Journal of Plant Pathology
214:Pseudocercosporella herpotrichoides
146:be the same when it does occur—the
13:
495:10.1111/j.1365-3059.1992.tb02331.x
250:
14:
1203:
432:Pulhalla JE, Mayfield JE (1974).
153:
124:
1156:
1155:
949:Evolution of sexual reproduction
257:evolution of sexual reproduction
706:
697:
280:
1057:Sexual reproduction in animals
538:
412:
295:
31:, is a nonsexual mechanism of
1:
731:
289:
929:Sex as a biological variable
912:Simultaneous hermaphroditism
178:
7:
604:10.1094/phyto.1997.87.3.284
10:
1208:
1067:Penile-vaginal intercourse
907:Sequential hermaphroditism
235:, and the human pathogens
43:in 1956 during studies on
23:, a process restricted to
1151:
1104:
937:
897:Testis-determining factor
794:
644:10.1080/07060668709501905
531:10.1017/s0016672300001245
510:"The parasexual cycle in
138:Mitotic chiasma formation
119:
838:Sex-determination system
786:
512:Verticillium albo-atrum
29:single-celled organisms
821:Sexual differentiation
382:Penicillium roqueforti
208:Verticillium alboatrum
192:Penicillium roqueforti
148:recombination of genes
863:Temperature-dependent
740:Introductory Mycology
479:Verticillium dahliae
436:Verticillium dahliae
418:Alexopolous (1996),
367:10.1094/phyto-73-952
351:Fusarium moniliforme
301:Alexopolous (1996),
202:Verticillium dahliae
186:Fusarium monoliforme
46:Aspergillus nidulans
1079:Hormonal motivation
1052:Fungal reproduction
971:Reproductive system
659:Cladosporium fulvum
628:Cladosporium fulvum
508:Hastie AC. (1964).
232:Cladosporium fulvum
51:Emericella nidulans
1192:Cellular processes
1187:Molecular genetics
1084:Human reproduction
1062:Sexual intercourse
1047:Plant reproduction
725:PMID 19465905
675:10.1007/bf00312643
558:(Ustilaginales)".
556:Ustilago scabiosae
398:10.1007/bf00351698
324:Deacon J. (2005).
244:Candida tropicalis
226:Magnaporthe grisea
220:Ustilago scabiosae
77:involving mitotic
1169:
1168:
1089:Lordosis behavior
804:Sexual dimorphism
518:Genetics Research
286:rDNA technology.
267:meiotic crossover
1199:
1159:
1158:
1119:Animal sexuality
1042:Sexual selection
781:
774:
767:
758:
757:
753:
726:
722:
713:
710:
704:
701:
695:
694:
663:Current Genetics
654:
648:
647:
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582:
576:
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551:
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536:
535:
533:
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499:
498:
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467:
457:
429:
423:
416:
410:
409:
386:Current Genetics
377:
371:
370:
346:
340:
339:
321:
306:
299:
273:species undergo
238:Candida albicans
195:(used in making
169:E. nidulans
41:Guido Pontecorvo
21:parasexual cycle
1207:
1206:
1202:
1201:
1200:
1198:
1197:
1196:
1172:
1171:
1170:
1165:
1147:
1134:Differentiation
1124:Human sexuality
1114:Plant sexuality
1100:
996:Spermatogenesis
940:
933:
796:
790:
785:
750:
734:
729:
723:
716:
711:
707:
702:
698:
669:(5–6): 508–11.
655:
651:
624:
620:
583:
579:
552:
548:
543:
539:
506:
502:
483:Plant Pathology
475:
471:
430:
426:
417:
413:
392:(4–5): 377–83.
378:
374:
347:
343:
336:
322:
309:
300:
296:
292:
283:
255:A study of the
253:
251:Candida species
181:
156:
140:
127:
122:
17:
12:
11:
5:
1205:
1195:
1194:
1189:
1184:
1167:
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1069:
1054:
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1039:
1038:
1037:
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1021:
1020:
1015:
1005:
1004:
1003:
998:
988:
983:
978:
973:
968:
963:
962:
961:
956:
945:
943:
935:
934:
932:
931:
926:
921:
916:
915:
914:
909:
899:
894:
893:
892:
887:
880:Sex chromosome
877:
872:
871:
870:
865:
860:
855:
850:
845:
835:
834:
833:
828:
818:
817:
816:
811:
800:
798:
792:
791:
784:
783:
776:
769:
761:
755:
754:
748:
733:
730:
728:
727:
714:
705:
696:
649:
618:
591:Phytopathology
577:
572:10.1086/297010
546:
537:
500:
469:
448:(3): 411–422.
424:
411:
372:
355:Phytopathology
341:
334:
326:Fungal Biology
307:
305:., pp. 196–97.
293:
291:
288:
282:
279:
252:
249:
180:
177:
160:nondisjunction
158:Occasionally,
155:
154:Haploidization
152:
139:
136:
126:
125:Diploidization
123:
121:
118:
83:haploidization
15:
9:
6:
4:
3:
2:
1204:
1193:
1190:
1188:
1185:
1183:
1180:
1179:
1177:
1162:
1154:
1153:
1150:
1140:
1137:
1135:
1132:
1130:
1127:
1126:
1125:
1122:
1121:
1120:
1117:
1115:
1112:
1111:
1109:
1107:
1103:
1095:
1094:Pelvic thrust
1092:
1090:
1087:
1085:
1082:
1080:
1077:
1075:
1072:
1068:
1065:
1064:
1063:
1060:
1059:
1058:
1055:
1053:
1050:
1048:
1045:
1043:
1040:
1036:
1033:
1031:
1028:
1027:
1026:
1025:Fertilization
1023:
1019:
1016:
1014:
1011:
1010:
1009:
1006:
1002:
999:
997:
994:
993:
992:
991:Gametogenesis
989:
987:
984:
982:
979:
977:
974:
972:
969:
967:
964:
960:
957:
955:
952:
951:
950:
947:
946:
944:
942:
936:
930:
927:
925:
924:parasexuality
922:
920:
917:
913:
910:
908:
905:
904:
903:
902:Hermaphrodite
900:
898:
895:
891:
888:
886:
883:
882:
881:
878:
876:
873:
869:
868:Haplodiploidy
866:
864:
861:
859:
856:
854:
851:
849:
846:
844:
841:
840:
839:
836:
832:
829:
827:
824:
823:
822:
819:
815:
812:
810:
807:
806:
805:
802:
801:
799:
793:
789:
782:
777:
775:
770:
768:
763:
762:
759:
751:
749:0-471-52229-5
745:
741:
736:
735:
721:
719:
709:
700:
692:
688:
684:
680:
676:
672:
668:
664:
660:
653:
645:
641:
637:
633:
629:
622:
614:
610:
605:
600:
597:(3): 284–94.
596:
592:
588:
581:
573:
569:
565:
561:
557:
550:
541:
532:
527:
524:(2): 305–15.
523:
519:
515:
513:
504:
496:
492:
489:(2): 141–47.
488:
484:
480:
473:
465:
461:
456:
451:
447:
443:
439:
437:
428:
421:
415:
407:
403:
399:
395:
391:
387:
383:
376:
368:
364:
361:(6): 952–55.
360:
356:
352:
345:
337:
335:1-4051-3066-0
331:
327:
320:
318:
316:
314:
312:
304:
298:
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287:
278:
276:
272:
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210:
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194:
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188:
187:
176:
172:
170:
166:
161:
151:
149:
144:
135:
132:
117:
115:
111:
106:
104:
98:
96:
92:
88:
84:
80:
79:crossing-over
76:
75:recombination
72:
68:
64:
60:
56:
52:
49:(also called
48:
47:
42:
38:
34:
33:parasexuality
30:
26:
22:
1013:spermatozoon
941:reproduction
923:
890:Y chromosome
885:X chromosome
831:Virilization
826:Feminization
739:
708:
699:
666:
662:
658:
652:
635:
631:
627:
621:
594:
590:
580:
563:
559:
555:
549:
540:
521:
517:
511:
503:
486:
482:
478:
472:
445:
441:
435:
427:
419:
414:
389:
385:
381:
375:
358:
354:
350:
344:
325:
302:
297:
284:
281:Significance
270:
261:
254:
242:
236:
230:
224:
218:
212:
206:
200:
197:blue cheeses
190:
184:
182:
173:
168:
164:
157:
141:
128:
107:
99:
50:
44:
32:
20:
18:
114:life cycles
87:chromosomes
63:anastomosis
1176:Categories
1074:Copulation
795:Biological
732:Cited text
566:: 98–101.
290:References
131:homologous
67:plasmogamy
55:teleomorph
1129:Mechanics
1106:Sexuality
1001:Oogenesis
976:Sex organ
966:Germ cell
954:Anisogamy
638:: 14–19.
422:., p. 12.
179:Organisms
165:aneuploid
95:genotypes
91:aneuploid
71:karyogamy
1182:Mycology
1161:Category
1139:Activity
1035:Internal
1030:External
919:Intersex
691:25780981
613:18945171
464:17248647
442:Genetics
406:30871714
986:Meiosis
959:Isogamy
683:8319310
455:1213075
275:meiosis
271:Candida
262:Candida
259:in six
143:Chiasma
110:somatic
103:mitosis
37:meiosis
1008:Gamete
981:Mating
939:Sexual
814:Female
746:
689:
681:
611:
462:
452:
404:
332:
120:Stages
59:hyphae
797:terms
687:S2CID
420:et al
402:S2CID
303:et al
25:fungi
1018:ovum
809:Male
744:ISBN
679:PMID
609:PMID
460:PMID
330:ISBN
241:and
81:and
27:and
19:The
788:Sex
671:doi
661:".
640:doi
630:".
599:doi
568:doi
564:153
526:doi
491:doi
481:".
450:PMC
394:doi
384:".
363:doi
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667:23
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