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  3. Identical twins possess exactly the same set of genes. Yet as they grow olde

Identical twins possess exactly the same set of genes. Yet as they grow olde

游客2023-12-19  66
问题     Identical twins possess exactly the same set of genes. Yet as they grow older,
they may begin to display subtle differences. They may start to look different,
develop different diseases or slide into different persons.                    【M1】______
Women who are identical twins may differ with their fertility or               【M2】______
the age at which they reach menopause. These discrepancies
usually attributed to ill-defined differences in environment.                  【M3】______
But a whole new level of explanation has been opened up by a generic survey    【M4】______
showing that identical twins, because they grow older, differ increasingly in  【M5】______
what is known as their epigenome. The term refers to natural
chemical modifications that occur in a person’s genome shortly before          【M6】______
conception and that act on a gcne as a gas pedal or a brake,
marking it for higher or lower activity.                                       【M7】______
Identical twins have the same set of epigenetic mark on the genome             【M8】______
when they are born. But differences in the epigenome disappear                 【M9】______
as the twins grow older and become greater the longer they live together,      【M10】______
say a team of researchers led by Dr. Manel Esteller of the Spanish National Cancer Center in Madrid. [br] 【M6】
选项
答案 before改成after
解析 词义理解和逻辑关系。这道题的考察实际上分为两部分，首先要理解“conception”的意义，如果按照平常的意义——“概念”来理解，显然是不正确的，因为通篇文章讲的是基因。实际上“conception”的动词原形“conceive”还有“孕育”的意思，由此而来的名词也就有了“受精”的含义。理解之后根据上下文判断应该是受精之后，而不是之前。因为之前的事件与双胞胎没有关系。同时，这道题由shortly也可以看出，因为没有“shortly before”的用法。
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