题干

一对表现型正常的夫妇,生了一个β地中海贫血症患儿.在他们欲生育第二胎时,发现妻子的双侧输卵管完全堵塞,不能完成体内受精.医生为该夫妇实施了体外受精和产前基因诊断,最终喜获一健康女婴.请回答:

(1)哺乳动物的体外受精主要包括____ 、____ 、____  等主要步骤.

(2)在对胎儿进行β地中海贫血症的产前基因诊断时,要先从羊水中的胎儿细胞提取DNA进行PCR扩增,然后用限制酶对扩增产物进行切割,产生多个片段的酶切产物,再根据不同长度的酶切产物在电泳时移动的速率不同,形成不同的电泳条带进行判断.

①PCR扩增与体内DNA复制过程中,解旋的方法不同,前者通过____解开双链,后者通过____解开双链.

②一种限制酶只能识别一种特定的核苷酸序列,大多数限制酶的识别序列由____ 个核苷酸组成.DNA分子经限制酶切割产生的DNA片段末端通常有两种形式,即黏性末端和平末端.当限制酶在它识别序列的中心轴线两侧将DNA的两条链分别切开时,产生的是____

③利用PCR扩增目的基因也是目的基因获取的方法之一,除此以外,目的基因还可以从基因文库中获取,基因文库包含________ 等类型,后者的基因中含有启动子.

④基因诊断的主要原理是____ .

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How to get siblings (兄弟姐妹) to get along

    One of the greatest gifts of parenthood is seeing your children form a relationship with each other that is independent of you. By giving hem someone else to play with, you can free up some time for yourself. Here are four techniques you can use to help your children appreciate each other while they're young.

    ⒈____ The No.1 thing parents can do to help their kids stay on good terms with each other is not to compare them with each other. Never say “Your sister never. . ”or “Why can't you do what your brother does?”____

    ⒉Try out of the way. Try not to get too involved in your kids' arguments. Learning cooperation and problem-solving is an important skill in life____And don't blame the older one for not “knowing better,” That puts pressure on the older child and leads to unhappiness.

    ⒊Activities and opportunities. Have your kids go to their siblings' games and activities____

    “My kids go to each other's activities, and take part in activities together,” says Patricia Walters-Fischer, mother of two. Not only do her children go, but they also offer support, encouraging each other before a big game or performance and offering comfort when things don't go well.

    ⒋Vacations. Don't ignore the value of a family vacation for bringing siblings together. When kids are away from their friends and forced to spend time together, they often enjoy each other____In fact, a weekend camping trip offers some of the best opportunities for working together, having fun and experiencing something new.

A. Never shout at them.

B. Don't compare.

C. It doesn't need to be anything extremely great.

D. That only serves to fuel the competition.

E. Give them a project, and they will learn how to work together.

F. They may need help solving a conflict, but try not to take sides.

G. Get them involved in one another's lives, so they can have a better appreciation of who their sibling is.