题干

AA和aa杂交所产生的F1通过连续自交直到Fn,则在此过程中(  )

A:AA和aa的亲本不含等位基因,杂交结果不符合分离定律

B:此过程共发生了n次等位基因的分离

C:杂交后代基因型频率保持不变

D:A和a的基因频率保持不变

上一题 下一题 0.0难度 选择题 更新时间:2019-09-12 09:00:06

答案(点此获取答案解析)

D

同类题1

Section B

Directions: Read the following passage. Answer the questions according to the information given in the passage.

    A wise teacher once told me that every teenager needs to experience a not-so-fun first job from working at a grocery store to the fast food industry.

    Now I still remember my first day at a fast food restaurant three years ago. I wanted to save up money and buy my own car, so I applied everywhere I could that summer. The restaurant called me right away and I thought to myself, this is going to be easy. Within four hours of my first shift (.轮班), I had angry customers who complained how slow I was. I watched in fear as a kid spilled his milk everywhere, and I heard the words that no 16-year-old boy or anyone for that matter wants to hear: "Mike, there's a problem in the men's bathroom and you might want gloves for this one." I realized right away that working at the restaurant was not going to be a picnic. The manager expected a clean environment and, particularly, fast service with a friendly smile.

    Over three years later I still work at that restaurant whenever I go home during vacations. I love my co-workers there and all the customers know who I am. Every morning the same senior citizens come in and get their morning coffees. They chat with us workers and joke around. Our smiles have just as much to do with them making us a part of their everyday lives as the coffee does.

    From my first job at the restaurant, I learned teamwork and devotion. I also learned staying positive no matter how rough things seem to get. I will forever carry the experience that I gained at the restaurant with me as I go forward in my life.