2021-2022英语周报60期答案

书面表达命题立意:本题要求学生给留学生朋友 Peter写封电子邮件,邀请他来你家做客。该情境基于学生实际生活,并融人了英语元素。该题很好地考查了学生的英语核心素养,同时也考查了学生的英语实际应用能力。根据要求应包含三个要点,内容可以适当扩充,增加一些细节。不要逐字翻译,机械照搬。参考范文Dear PeterWe haven t seen each other for a long time, so i want to invite you to my home next weekend. My home islocated at Zhongshan Road near the city library. You can take a bus in front of your school to get there.To have an interesting get-together. I will arrange some activities for us to enjoy, such as drinking Chinesetea and learning to make dumplings. In addition. watching some performances of Peking opera will also be agood choice.I have many things to talk with you. so I hope you can accept my invitation. I promise you will have a goodtime at my home. Please reply to me with your decision.Yours

20.(1)将亮红眼雌果蝇与野生型雄果蝇杂交,所得F1雄果蝇与母本回交,从F2中得到亮红眼雄果蝇(4分)(2)①亮红眼:猩红眼=3:1(或亮红眼:猩红眼=3:1,亮红眼早:猩红眼早=3:1)(2分)2号(2分)深红眼:亮红眼=3:1(2分)②4(2分)4(2分)【解析】本题主要考查遗传的基本规律,考查学生的获取信息的能力、实验与探究能力和综合运用能力。1)为繁殖大量亮红眼雄果蝇,将亮红眼雌果蝇与野生型雄果蝇杂交,所得F:雄果蝇与母本回交,从F中得到亮红眼雄果蝇。F1相互交配,F2中所得亮红眼雄果蝇所占的比例较小。(2)①甲组F2的表现型和比例为亮红眼:猩红眼=3:1,说明亮红眼与猩红眼的遗传遵循分离定律,即受到一对等位基因的控制,则可确定亮红眼基因位于2号染色体上。若亮红眼雌果蝇(stst)与野生型雄果蝇(STST)杂交获得F1,F1的雌雄果蝇自山交配,则子代的表现型和比例为深红眼:亮红眼=3:1。②乙组的杂交实验结果中,F2的比例为深红眼:亮红眼:朱红眼=6:4:6,符合自由组合定律。设控制亮红眼的基因为st,则亲本亮红眼雄果蝇的基因型为st'stXY,朱红眼雌果蝇的基因型为 STSTXX,杂交后F1深红眼果蝇的基因型为STst'XX,朱红眼果蝇的基因型为 STst'XY。F1雌雄果蝇杂交后,F2果蝇中基因型为ST_XX"STXY的表现为深红眼,占6/16;基因型为stst的表现为亮红眼,占4/16;基因型为STXX、STXY的表现为朱红眼,占6/16,所以F2深红眼果蝇和亮红眼果蝇的基因型各有4种。

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