2018-2022英语周报29答案

17.(12分,除标注外,每空2分)(1)1(1分)两对(1分)(2)7全部开蓝花红花:蓝花=3:1(3)第一年:将杂交组合1亲本杂交获得的种子种植,育成植株,让其自交并收获种子。(1分)第二年:将收获种子分开种植,育成植株,让其自交,选择颜色更深观赏性好的蓝色花植株,收获其种子,即为所需的种子(3分)解析】(1)杂交组合1的F2表现型为红色:蓝色≈13:3,是自由组合比9:3:3:1的变形,红色和蓝色这对相对性状受两对等位基因控制。设相关基因用A、a和B、b表示,仅含有其中一种单显性基因(A或B)的个体表现型为蓝色,其余7种基因型个体表现为红色。(2)杂交组合1的F1基因型可表示为AaBb,表现型为红色;F2中有7种基因型个体表现为红色。杂交组合2的F2中,蓝色个体的基因型可表示为aBB(或AAbb),自交后代全为蓝色;杂交组合2的F1中,红色个体的基因型可表示为AaBB(或AABb),将两个杂交组合的F1植株杂交,子代的表现型及比例为红花:蓝花=3:1。(3)纯合蓝色花品种的基因型可表示为aaBB(或AAb),杂交组合1的F1基因型可表示为AaBb,将基因型为AaBb的种子种植,育成植株,收获种子,第二年将种子分开种植,育成植株,让其自交,选择颜色更深观赏性好的蓝色花植株,收获其种子,即为所需的种子。

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

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