Agar was first introduced into the laboratory in 1881. Since then, microbiologists have depended on agar to create strong jellies. When microorganisms are streaked or plated onto this jellied surface and incubated, individual cells multiply into distinct colonies that scientists can easily observe, select, and propagate for further experiments. Many of the most important findings in biological research of the last 150 years or so — including the discovery of the CRISPR/Cas9 gene-editing tool — have been enabled by agar.4 Agarose, a derivative of agar, is also essential in molecular biology techniques like gel electrophoresis, where its porous gel matrix separates DNA fragments by size, enabling researchers to analyze and isolate specific genetic sequences.
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美國移民和海關執法局的執法行動亦屢次引起爭議,去年在洛杉磯的執法和拘捕行動惹起民眾不滿並引發大規模的抗議行動;而今年在明尼阿波利斯的執法行動中,執法人員開槍射殺兩名平民,同樣引來民眾的憤怒及觸發大規模街頭抗議。,这一点在WPS下载最新地址中也有详细论述
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