2021-2022 英语周报 七年级 广州答案

第一节短文改错(共10小题,每小题1分,满分10分)Michael. who now studied in our school. is my good friend. On the morning of laststudiesSaturday he asked me A spend the weekend together with himself. It was such fine weatherhimthat we had decided to hang around in the town. There were lots of pcople walk hereand there. Michael looked interesting in everything he saw. Three hours went by before weinterestedboth felt hungrily. but all the restaurant were full of guests. To our excitement. we werehrestaurantsabout to give up while two guests rose and left. We immediately sat down for our lunchhenand about an hour later we took the taxi home

38.(15分,除标注外,每空2分)(1)DNA对人体无毒、有一个至多个限制酶切割位点、能在宿主细胞中复制、有标记基因(3分)(写出两点即得分)(2)逆转录无非编码序列(3)转录和翮译抗原体液免疫和细胞(或“特异性”)【解析】(1)运载体是婁将的基因送入绌胞中,因此,作为运载体的质粒、λ噬菌体的衍生物、动植物病毒,或者本身就为DNA,或含有DNA,这样才能与目的基因拼接。许多病毒对人体有一定的危害,腺病毒载体重组新冠病毒疫苗要进入人体,所以,改造后的腺病毒必须是无毒的,另外,作为运载体必须只备以下三个特点:有一至多个限制酶切割位点,供外源DNA片段插入其中;携带外源DNA片段进入受体细胞后在细胞中进行复制;有标记基因供重组DNA的鉴定和选择。(2)从RNA形成DNA需要经逆转录酶的催化,经RNA逆转录成的DNA是不含非编码区和内含于的(3)基因的表达有两个过程,即转录和翻译,疫苗中的S蛋自为抗原,进入体内后经特异性兔疫(包括体液免疫秈细胞免疫)过程形成记忆细胞和抗休。注射疫苗后,当新冠病毒进入人体时,记忆细胞可快速增殖分化出浆细胞和效应T细胞,浆细胞再产生大量抗休,对抗侵入人体的病毒

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