2022英语周报外研七年级上册答案

2022-08-19 09:55 
衡水金卷2021答案 衡水金卷2021答案

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捕食害虫,使该环境中害虫种群32.【答案】(1)两(1分)该种植物控制花色的这对相对性状的两对等位基因位于两对常染色体上,人工诱变引起这两对等位基因中至少其中一对发生隐性突变,两对基因中有至少一对为隐性则表现为白花性状。(4分(2)13(2分)能(1分)若选择F2中基因型为aBB和Abb的白花植株进行杂交,后代全为红花植株(2分)(3) AaBbx Aabb或 AaBbxaaBb(2分)【解析】(1)由上述实验F2中雌雄植株表现型都为红花:白花=97,可推出这对相对性状应由两对等位基因控制,且位于两对同源染色体上,并遵循自由组合定律,由实验结果可以推断只有两对基因都为显性才开红花,其他的开白花,所以人工诱变引起这两对等位基因中至少其中一对基因发生隐性突变,两对基因中有至少对为隐性则表现为白花。(2)F2中纯合红花植株AABB占116,纯合白花植株三种基因型分别为aB、AAb、abb,共占3/16,所以F2纯合红花植株与纯合白花植株的比例为1:3;选择F2中基因型为aBB和AAb的白花植株进行交配,可以使后代全为红花植株。(3)若F2中随机选择一株红花植株(AB)和一株白花植株杂交,后代红花植株(AB)占38,应该为34×12,即亲本的基因型应为 AaaA、Bb×bb或者Aa×a、Bb×Bb,所以杂交组合基因型应为 AaBbx Aabb或者AaBb×aBb

2022英语周报外研七年级上册答案

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