小明患有色盲，而他的父母色觉正常．你认为小明的色盲基因来自（

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问题选择题

小明患有色盲，而他的父母色觉正常．你认为小明的色盲基因来自（　　）

A．父亲

B．父亲和母亲

C．母亲

D．不能确定

答案

在亲代的生殖细胞形成过程中，经过减数分裂，两条性染色体彼此分离，男性产生两种类型的精子--含X染色体的精子和含Y染色体的精子．女性则只产一种含X染色体的卵细胞．受精时，如果是含X的精子与卵子结合，就产生具有XX的受精卵并发育成女性；如果是含Y的精子与卵子结合，就产生具有XY的受精卵并发育成为男性．受精卵中的基因一半来自父亲，一半来自母亲；男孩的X一定来源母亲，Y一定来源于父亲．色盲基因在X染色体上，色盲由隐性基因控制．因此男孩的色盲基因来自母亲的X染色体．

故选：C

阅读理解

Today just as technology changed the face of industry, farms have experienced an “agricultural revolution”. On the farm of today, machines provide almost all the power.

One of the most important benefits will be the farm puter. A few forward-looking farmers are already using puters to help them run their farms more efficiently. The puters help them keep more accurate records so they can make better decisions on what crops to plant, how much livestock(家畜) to buy, when to sell their products, and how much profit they can expect. Many puter panies have been developing special puter programs just for farmers. Programs are being written for pig producers, grain farmers, potato farmers, and dairy farmers. In the future, farmers will be able to purchase puter programs made to their needs. Because of the growing importance of puters on the farm, students at agricultural colleges are required to take puter classes in addition to their normal agricultural courses. There can be no doubt that farmers will rely on puters even more in the future. While the old-time farm depended on horse power, and modern farms depend on machine power, farms of the future will depend on puter power.

Another technological advance which is still in the experimental stage is the robot, a real “mechanized hired hand” that will be able to move and, in some ways, think like a human being. Agricultural engineers believe that puter-aided robots will make shocking changes in farming before the end of the century. Unlike farmers of the present, farmers of the future will find that many day-to-day tasks will be done for them. Scientists are now developing robots that will be able to shear（修剪） sheep, drive tractors, and harvest fruit. Even plex jobs will be done by robots. For example, in order to milk their cows, farmers must first drive them into the barn, then connect them to the milking machines, watch the machines, and disconnect them when they are finished. In the future, this will all be done by robots. In addition, when the milking is pleted, the robots will automatically check to make sure that the milk is pure. The plete change of the farm is far in the future, but engineers expect that some robots will be used before long.