目前已知环境或食物中的许多化学物质是动物和/或人类的致癌物。检验致突变作用的生物学试验(如著名的 Ames 试验)表明,许多化学致癌物同时也是致突变物,反之亦然。经分子遗传学研究证明,一般这类物质引起点突变,即 DNA 的核苷酸序列发生改变。Cairns 却提出一种假说,认为人类许多种肿瘤不是点突变,而是染色体畸变引起,有些染色体结构上的改变甚至可在显微镜下观察到。 Many chemicals that are currently known in the environment or food are animal and/or human carcinogens. Biological tests that test mutagenesis (such as the well-known Ames test) show that many chemical carcinogens are also mutagens, and vice versa. Molecular genetic studies have shown that this type of substance generally causes point mutations, ie changes in the nucleotide sequence of the DNA. Cairns put forward a hypothesis that many human tumors are not point mutations, but chromosomal aberrations. Some structural changes in chromosomes can even be observed under the microscope.