3、胚胎移植技术的应用为大量繁育良种奶牛带来了光明的前景。这项技术的操作过程大致如图所示。请回答:
(1)为了促使良种母牛排卵,育种家们应给母牛注射促性腺激素。为了使早期胚胎顺利地在接受胚胎的母牛子宫内膜上着床,应事先给该母牛注射孕激素。
(2)选择良种公牛的精子时,应选择含X染色体的精子才可繁育出良种奶牛。
(3)把受精卵培育成早期胚胎过程中,应使用的培养基是培养液。
(4)胚胎移植技术除了快速繁育良种家畜外,还可用于哪些方面(至少答出两个方面)?
①克隆哺乳动物;②培育转基因动物,保存珍稀哺乳动物;③保护生物的多样性;④克服人类的不孕症等(任意两项即可)。
[高考模拟]
2、为了大力发展我国的肉牛和奶牛养殖业,科学家们在育种途径中进行了大胆探索,并取得了初步成果。
Ⅰ、2002年1月中旬到2月中旬,中国自主完成的首批成年体细胞克隆牛在山东曹县五里墩陆续降生。克隆牛有3个母亲,A牛提供细胞核即供体细胞,B牛提供去除细胞核的卵细胞即受体细胞,两种细胞在电脉冲的刺激下融合之后,通过细胞分裂形成早期胚胎,再将这个胚胎植入C牛子宫内。请回答下列问题:
(1)培养出的克隆牛几乎是A牛复制品。这是因为控制牛性状遗传的物质主要存在于细胞核中。
(2)如果多个供体细胞来自同一头牛,培育的这些牛在性状上也不完全相同,分析其原因:
①性状变异可由环境条件引起; ②受体细胞的细胞质基因不同;
③基因可能会发生突变。
Ⅱ、在克隆技术出现之前,育种工作者已经开始采用胚胎分割移植的方法尽快繁育更多的优质牛。这种育种技术的主要步骤是:将经过人工授精得到的受精卵在试管内培养到8个细胞的胚胎时,进行胚胎分割,均分为4等份,再分别移植到多头母牛的子宫内发育、分娩,就能得到多头所需要的小牛。
(3)胚胎分割移植在受精卵培养到8个细胞的卵裂期时进行,其主要原因是此时还未出现细胞的分化。
(4)通过胚胎分割移植培育出的这些小牛,其性别表现为全为雌性或全为雄性。
(5)通过体细胞克隆技术培育的小牛,其性别取决于供体细胞。
(一)体外受精和胚胎体外培养 (二)胚胎移植培育流程
(三)胚胎分割的流程
[基础训练]
1、下列属于有性生殖的是( A )
A、试管婴儿 B、胚胎分割 C、克隆 D、胚胎干细胞培养
(二)早期胚胎发育
根据胚胎形态的变化,可将早期发育的胚胎分为以下几个阶段:
(一)受精作用
1、动物个体发育的起点:受精卵。
2、过程:精卵识别、精子附着于卵膜、精卵质膜融合等过程。
3、同种动物精卵才能结合的原因:精子和卵细胞表面有特异性相互识别的蛋白。
3.本文要注意,概要一定要根据文段的时态来写。同时,绝对不能抄袭原文的句子。文章是讨论你看完这个故事后,你如何评价这位老师的无私行为以及你的想法,属于是评论性文字和结论性的观点,故用一般现在时或一般将来时态。
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[答案]
Greatest Love is Unselfish
During Wenchuan Earthquake in Sichuan Province, a rescue team found a teacher, dead for hours, and four school kids, safe with the protection of the teacher. And the teacher's greatest love gave everyone a great shock.
A very ordinary teacher would rather give his life to save and protect his students, for he knew that he was a teacher and should protect his students, As we know, when the disaster broke out, all the teachers in this earthquake area made their efforts to help and save their students, and this noble act shows that greatest love is unselfish. Facing natural disasters, sometimes we human beings may feel too weak, but just at this very moment, we will try everything to help others, even devote our lives to doing that.
After reading the news story, I was moved to tears. Greatest love is unselfish. The teacher's action illustrates our kind teachers' greatest love to their students.
2.本文的概要必须包含以下要点:The rescue teamers made their efforts to rescue the victims buried in the ruins. They found four school kids were under a teacher's desk and the teacher placed himself to the side of the desk without boards, protecting his students from harm. / but the teacher chose to give the living chances to his lovely students.
1.写作有可能用到的主要短语和单词:自然灾害natural disasters,保护 protect/protection,奉献某A的生命devote one' s life to doing sth,努力做某事make one' s efforts to do sth,救某生命save one ' s life.
2.作文中不能出现真实姓名和学校名称。
[评分标准]概括准确,语言规范,内容合适,篇章连贯。
[写作辅导]
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