问题 填空题

YJ17回丝装置主回丝输送带将副回丝输送带输送过来的烟丝输送至后部()上。

答案

参考答案:落丝振槽

填空题

在生命科学研究领域,正确的思路和研究方法往往是科学家们成功的关键。请分析回答下列问题:

(1)孟德尔对豌豆的七对相对性状的杂交实验中,F1的表现型都各只有一种,F2都产生接近3:1的性状分离比。为解释上述实验结果,孟德尔提出了哪些假设:_____________。这些假设完美地解释了上述实验现象。但作为一种假设,还要能够预期另一些实验结果以证实假设的正确性。

(2)孟德尔设计了_______实验。以高茎和矮茎这一相对性状为例,该实验结果的预期是___________。实验选用隐性亲本与F1杂交,是因为隐性亲本的隐性基因对F1产生的配子的基因________________,所以根据测交后代的性状表现,可推测F1产生的配子中含有什么基因。

(3)孟德尔对豌豆的七对相对性状的杂交实验中,F2产生3:1的性状分离比需要满足哪些条件:_____。

A.所研究的每一对相对性状只受一对等位基因控制,且等位基因要完全显性

B.F1产生两种类型的配子,且所有配子发育良好,受精机会均等

C.所有后代可以处于不同的环境中,只需存活率相同

D.供试验群体要大,个体数量足够多

(4)孟德尔运用______________法,归纳得出了遗传的两大定律为杂交育种提供了理论基础。如利用纯种高秆(显性)抗锈病(显性)小麦和矮秆不抗锈病小麦可培育成矮秆抗锈病小麦。选种要从_______开始。杂交育种只适合于进行___________的生物。

单项选择题

Many people who work in London prefer to live outside it, and to go in to their offices or schools every day by train, car or bus, even though this means they have to get up early in the morning and reach home late in the evening.

One advantage of living outside London is that houses are cheaper. Even a small flat in London without a garden costs quite a lot to rent. With the same money, one can get a little house in the country with a garden of one’s own.

Then, in the country one can rest from the noise and hurry of the town. Even though one has to get up earlier and spend more time in trains or buses, one can sleep better at night and during weekends and on summer evenings, one can enjoy the fresh, clean air of the country. If one likes gardens, one can spend one’s free time digging, planting, watering and doing the hundred and one other jobs which are needed in a garden. Then, when the flowers and vegetables come up, one has the reward of one who has shared the secret of Nature.

Some people, however, take no interest in country things: for them, happiness lies in the town, with its cinemas and theatres, beautiful shops and busy streets, dance-hails and restaurants. Such people would feel that their life was not worth living if they had to live it outside London. An occasional walk in one of the parks and a fortnight’s (two weeks) visit to the sea every summer is all the country they want. the rest they are quite prepared to leave to those who are glad to get away from London every night.

One can use the same money for()to buy a little house with a garden in the country.

A. getting a small flat with a garden

B. having a small flat with a garden

C. renting a small flat without a garden

D. buying a small flat without a garden