题目内容

真核生物的染色体主要是由、和__组成的。

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病毒的遗传因子可包括1～300个基因。与生命有机体不同，病毒的遗传因子可能是DNA或RNA，(但不可能同时兼有!)因此DNA不是完全通用的遗传物质。

Girls flinch back in the competition with boys most probably because
[A] they are short of confidence in themselves.
[B] employers often prefer boys to take technical jobs.
[C] they have poorer performance in technical jobs.
[D] they are willing to leave technical jobs to boys.

从4种不同的物种分离出的核酸中各种碱基的比率(%)如下：
(1)对于每个物种，回答：①核酸是DNA还是RNA？②它是双链还是单链？
(2)填充物种4中缺少的碱基百分比。

[A] immigration policies.
[B] organized crime and violence.
[C] U.S./Mexico broader security.
[D] trade between the two countries.