质粒与染色体DNA一样,失去质粒,细菌细胞就会死亡。
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在进行菌种保藏工作时,一般选用优良纯种的休眠体,为其提供一个营养充分利于生长的环境条件。
A. 对
B. 错
I PrepareDuring the battle againstnovel coronavirus, medical workers, scientists and volunteers are always on the frontlines. They are regarded as .
A. heroes
B. role models
C. heroes in harm’s way
I PreparePresident Xi Jinping used three words to describe the distinct characters of hero models: , persistence, and simplicity.
A. loyalty
B. integrity
C. honesty