2018-2022 英语周报 高二 新课程 47答案

书面表达One possible versionI求Dear PeterI heve good news for you Our school Food Club will hold a dumpling- making activity. As you're interestedin Chinese food, I'm writing to invite you to join in the activity with me.As a kind of traditional Chinese food, dumplings are very popular during festivals, especially in the SpringFestival, when people will get together to make dumplings. The activity will begin at g am next Saturday in theschool canteen. First, (chefs) will teach us how to make dumplings step by step. Then, there will be a dumplingmaking competition in groups. Finally comes the most exciting part--enyoying our dumplings.Looking forward to your coming.Your

22.(12分,每空2分)(1)先杂交后子代自交3:1(2)DDd35:1(3)1:11/2【解析】(1)如果遗传因子不是独立遗传而是融合遗传的,则亲本先杂交后自交,由于F1将不一定形成11配子种类比,所以F2将不会严格的出现3:1的氵性状分离比。(2)如果体细胞中遗传因子不是成对存在的,而是纯合个体的体细胞中每种遗传因子有4个,则F1的基因型为DDd,表现型是高茎;F1产生的配子为DD:Dddd=1:4:1,F2中高茎:矮茎=(1-1/6×1/6):(1/6×1/6)=35:1。(3)如果雌;雄配子不是随机结合的,而是相同种类的配子才能结合,则F2基因型及其比例为DD:dd=:1,即高茎:矮茎=1:1;如果雌、雄配子存活率不同,F2中高茎:矮茎=5:1,即矮茎占1/6=1/21/3,由此说明d的花粉有50%不育,即雄配子中d占1/3,符合上述分式的拆分。

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