异源多倍体(种间杂交杂种染色体加倍)

异源多倍体（种间杂交—杂种染色体加倍）：Allopolyploids：allopolyploidareformedfromhybridsbetweencloselyrelatedspecies.ThedifferentsetsofchromosomesaresufficientlydifferentinDNAsequencenottopairbetweensetsinmeiosis.Thechromosomenumberdoublesaccidentallybyfailedmitosissothateachcellhastwocompletesetsofchromosomesfromeachparent,andthesepairlikewithlike,restoringfertility.e.g.萝卜甘蓝萝卜(2x=18)×甘蓝(2x=18)F1杂种(2n=2x=18=9+9)9条来自萝卜—R;9条来自甘蓝—B.F1-RB无对应同源染色体，减Ⅰ不配对，形成18个单价体，随机分离不均衡，配子几乎全部不育偶尔可育(18个单价体在一个配子中）自交F2株型大，根像萝卜，叶像甘蓝，且可育2n=4x=36=(9+9)x2F2(RRBB)(36)可育配子（18=9R+9B）异源六倍体小麦的形成：AAxBB(2n=2x=14)(2n=2x=14)AB不育配子，加倍AABBxDD（2n=4x=28)(2n=2x=14)ABD(2n=3x=21)不育配子，加倍AABBDD（2n=6x=42)可育异源六倍体小麦e.g.小黑麦（异源八倍体）普通六倍体小麦AABBDD×RR二倍体黑麦6x=422x=14配子ABDRF1ABDR28（21+7）染色体加倍AABBDDRR(8x=56)e.g.无籽西瓜(同源三倍体)：西瓜苗期（2x=22）秋水仙素处理（4x=44）母本4x×2x父本F13x=33二倍体花粉刺激无籽果实发育多倍体的诱发：物理化学0.01%~1.0%的秋水仙素诱导6.2.2Aneuploidy非整倍体Aneuploidyreferstosmalldeviationsfromthechromosomenumbersoftheseries.染色体非整倍数改变：核内染色体数通常以二倍体(2x)染色体数作为标准，在此基础上增减个别几条染色体非整倍体Monosome(单体)2x-1(ABCD)(ABC)缺一条Trisomy(三体)2x+1(ABCD)(ABCD)(A)多一条Tetrasomy(四体)2x+2(ABCD)(ABCD)(AA)多相同2条Ditrisomy(双三体)2x+1+1(ABCD)(ABCD)(AB)各多一条Nullisomic(缺体)2x-2(ABC)(ABC)缺相同两条Aneuploidaberrance：infertile*大多数动植物单体都不能存活黑腹果蝇(2x=8)X，Y染色体（I）:多/少1条影响生育V形染色体（II、III）:多/少1条致死点状染色体（IV）:多（三体2x+1=9）/少1条（单体2x-1=7）可以存活、繁殖人(2n=46)常染色体三体(2n+1=47)胚胎期致死—自发性流产21三体先天愚型（Down’ssyndrome–唐氏综合症，1/750）常染色体单体(2n-1=45)致死性染色体单体XO（Turner’ssyndrome-特纳氏综合症，1/10000）YO不能存活三体XXX（1/2000）、XXY（1/2000）四体XXXX、XXYY可存活但表型异常Aneuploidgametesarisefromerrorsatbothfirstandseconddivisionofmeiosisthroughaprocessknownasnondisjunction.ThisiswhereeithertwohomologouschromosomesfailtoseparateatmeiosisIoracentromerefailstosplitatmetaphaseofmeiosisII.