问题 填空题

现有A和B两个肉牛品种,A品种牛的细胞组成可表示为A细胞核、A细胞质,B品种牛则为B细胞核、B细胞质。

(1)如果要获得一头克隆牛,使其细胞由A细胞核和B细胞质组成,基本步骤是:从A品种牛体内取出体细胞,进行体外培养。然后再从培养细胞中取出_______注入B品种牛的______卵母细胞中,经过某种刺激和培养后,可形成胚胎,该胚胎被称为_________。将该胚胎移入代孕母牛的_______中,通过培育可达到目的。

(2)一般来说,要想大量获得这种克隆牛比较困难,原因之一是卵母细胞的数量_____,为解决这一问题,可以用_____激素处理B品种母牛。

(3)克隆牛的产生说明______具有全能性。克隆牛的性状主要表现______品种牛的特征。由A、B两品种杂交得到的牛与克隆牛相比,杂交牛细胞核的遗传物质来自______个亲本,细胞质来自______性亲本,克隆牛和杂交牛的遗传物质组成_______(填“相同”或“不同”)。

答案

(1)A品种牛的细胞核     去核      重组胚胎     子宫

(2)不足     促性腺

(3)动物体细胞核     A      两     雌     不同

单项选择题

Teachers need to be aware of the emotional, intellectual, and physical changes that younga-duhs experience. And they also need to give serious (91) to how they can best (92) such changes. Growing bodies need movement and (93) , but not just in ways that emphasize competition. (94) they are adjusting to their new bodies and a whole host of new intellectual and emotional challenges, teenagers are especially self-conscious and need the (95) that comes from achieving success and knowing that their accomplishments are (96) by others. However, the typical teenage lifestyle is already filled with so much competition that it would be (97) to plan activities in which there are more winners than losers, (98) , publishing newsletters with many student-written book reviews, (99) student artwork, and sponsoring book discussion clubs. A variety of small clubs can provide (100) opportunities for leadership, as well as for practice in successful (101) dynamics. Making friends is extremely important to teenagers, and many shy students need the (102) of some kind of organization with a supportive adult (103) visible in the background.
In these activities, it is important to remember that young teens have (104) attention spans. A variety of activities should be organized (105) participants can remain active as long as they want and then go on to (106) else without feeling guilty and without letting the other participants (107) This does not mean that adults must accept irresponsibility. (108) , they can help students acquire a sense of commitment by (109) for roles that are within their (110) and their attention spans and by having clearly stated rules.

A.everything

B.anything

C.nothing

D.something

单项选择题