题干

下列有关减数分裂及受精相关知识的说法错误的是 (     )

A:基因型为AaBb(独立遗传)的雄性动物,其精巢内的精原细胞经减数分裂形成精子的基因型AB,ab,Ab,aB

B:一个基因型为AaXbY的精原细胞,在减数分裂过程中,由于染色体分配错乱,产生了一个AAaY的精子,则其它三个精子的基因型分别是aY、Xb、Xb

C:细胞正常分裂的情况下,果蝇有丝分裂后期的精原细胞和减数第二次分裂后期的次级精母细胞一定含有两条Y染色体

D:减数分裂和受精作用可维持前后代染色体数目恒定

上一题 下一题 0.0难度 选择题 更新时间:2018-04-24 10:15:38

答案(点此获取答案解析)

C

同类题5

阅读下面材料,从每题所给的A、B、C、D四个选项中选出最佳选项。

B

    Have you ever stayed in a hotel? Most Chinese hotels often provide guests with things like disposable (一次性的) toothbrushes, toothpaste, shampoo and slippers. Many guests like the idea because they don't have to bring their own. But, if you travel to Beijing, remember to bring your own things. Starting from June, some hotels in Beijing will no longer provide guests with these disposables. They want to ask people to use less disposable things.

    Many disposable things are made of plastic. People throw them away after only using them once. It is a waste of natural resources (资源) and is very bad for the environment. Do you know, one Chinese person makes as much as 400kg of waste a year! Most of that waste comes from disposable things. In Beijing, people throw away about 19,000 tons of plastic bags and 1,320 tons of plastic lunch bowls every year! Plastic can take between 100 and 400 years to break down. So the less plastic we throw out, the better. So, wherever you travel, bring your own things and use them again and again.

    Back at home and school, you can also do something to make our world a better place. Try to do these things in your daily life: Use cloth shopping bags, not plastic ones. After using a plastic bag, wash it out and let it dry. Then you can use it over and over again. Do not use paper cups. At your school canteen(食堂), use your own bowl and chopsticks instead of disposable ones.