发布时间 : 星期三 文章07染色体畸变1 - 图文更新完毕开始阅读
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同源四倍体二显体的基因分离方式及形成配子的比例：
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Gene segregation in a tetraploid showing orderly pairing by bivalents 幻灯片117
Gametes and phenotypes ratios
? As shows, the 2x gametes produced are A/a, A/A, or a/a, in a ratio of 8:2:2, or 4:1:1. If such a
plant is selfed, the probability of an a/a/a/a phenotype in the offspring is 1/6 × 1/6 =1/36. In other words, a 35:1 phenotypic ratio of A/–/–/–:a/a/a/a will be observed if A is fully dominant over three alleles.
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同源四倍体某座位的等位基因按染色体随机分离
基因型 配子种类和比例 自交子代基因型 自交后代比例
AA Aa aa A4 A3a A2a2 Aa3 a4 A a
AAAa 1 1 1 2 1 全部
AAaa 1 4 1 1 8 18 8 1 35 1
Aaaa 1 1 1 2 1 3 1
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异源多倍体（allopolyploid):
两个或两个以上的不相同的物种杂交，它们的杂种经过染色体加倍形成的多倍体。 普通小麦、棉花、烟草、油菜、甘蔗
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allopolyploids
? The “classic” allopolyploid was synthesized by G. Karpechenko in 1928. He wanted to
make a fertile hybrid that would have the leaves of the cabbage (Brassica) and the roots of the radish (Raphanus). Each of these species has 18 chromosomes, and they are related closely enough to allow intercrossing.
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The origin of the amphidiploid (Raphanobrassica) formed from cabbage (Brassica) and radish (Raphanus)
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? 例：普通烟草的产生：
? 拟茸毛烟草 × 美花烟草 2n=2X=TT=24=12Ⅱ ↓
2n=2X=SS=24=12Ⅱ F1:
2n=2X=TS=24=12Ⅰ+12Ⅰ ? ↓加倍 ? 普通烟草（双二倍体） ? 2n=4X=TTSS=48=12Ⅱ+12Ⅱ 偶倍数异源多倍体在减数分裂时能象二倍体一样联会成二价体，故异源多倍体可表现出与二倍体相同的性状遗传规律。