问题
问答题 简答题
为什么单交换最多只能产生50%的重组基因型？
答案
参考答案：
（1）性母细胞通过减数分裂产生配子的时侯，不是100%的要发生交换；
（2）发生单交换所产生的配子中，只有50%是重组类型。
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为什么单交换最多只能产生50%的重组基因型？
参考答案：
（1）性母细胞通过减数分裂产生配子的时侯，不是100%的要发生交换；
（2）发生单交换所产生的配子中，只有50%是重组类型。
| 完形填空。 | |||
| I work in a small shop. It is near __1__ English school. Every day students come to __2__ things in the shop. __3__ the morning, I get up at six, and then I have __4__. I go to work __5__ my bike. I get to (达到) the shop at about six forty. The shop __6__ from 7:00 a.m. to 7:00 p.m. We __7__ many things like food and drinks. We have school things, __8__ . So __9__ many people in our __10__ from morning to evening. | |||
| ( ) 1. A. / ( ) 2. A. buy ( ) 3. A. On ( ) 4. A. food ( ) 5. A. from ( ) 6. A. open ( ) 7. A. sells ( ) 8. A. too ( ) 9. A. there is ( ) 10. A. shop | B. a B. play B. At B. lunch B. on B. eats B. to sell B. two B. there are B. home | C. an C. like C. In C. dinner C. at C. has C. sell C. and C. there has C. school | D. the D. look D. For D. breakfast D. by D. is open D. selling D. but D. there have D. family |