问题 问答题 简答题

近交系的基础群与生产群有何不同?

答案

参考答案:

近交系的基础群采用全同胞兄妹进行交配,基础群的动物应有繁殖系谱,每—代有限定的留种对数,有个体纪录卡(包括品系名称、近交代数、动物编号、出生日期、双亲编号、离乳日期、交配日期,生育记录等)。基础群动物不超过5-7代都应能追溯到一对共同的祖先。而生产群动物来自基础群或血缘扩大群,通常选用红绿灯生产体系,采用随机交配方式进行繁殖,繁殖代数一般不超过四代,四代以后的动物不再留种。

选择题
单项选择题

All her life, my mother wanted busy children. It was very important that her house should remain at all times clean and tidy.
You could turn your back for a moment in my mother’s house, leave a half written letter on the dining table, a magazine open on the chair, and turn around to find that my mother had "put it back where it belonged," as she explained. My wife, on one of her first visits to my mother’s house, placed a packet of biscuits on an end table and went to the kitchen to fetch a drink. When she returned, she found the packet had been removed. Confused, she set down her drink and went back to the kitchen for more biscuits, only to return to find that her drink had disappeared. Up to then she had guessed that everyone in my family held onto their drinks so as not to make water rings on the end tables. Now she knows better.
These disappearances had a confusing effect on our family. We were all inclined to forgetfulness, and it was common for one of us, upon returning from the bathroom, to find the every sign of his work in progress had disappeared suddenly. "Do you remember what I was doing" was a question frequently asked, but rarely answered.
Now my sister has developed a secondhand love of clean windows, and my brother does the cleaning in his house, perhaps to avoid having to be the one to lift his feet. I try not to think about it too much, but I have at this later time started to dust the furniture once a week.

Which of the following is TRUE about my mother

A.She enjoyed removing others’ drinks.
B.She became more and more forgetful.
C.She preferred to do everything by herself.
D.She wanted to keep her house in good order.