“母生十子,十子不一”是一种普遍的生物现象。这种现象的实质是亲代与后代及后代不同个体间在性状表现上存在差异。同一父母的孩子,在长相、性格及脾气等方面有相似也有相异,就是同卵双生的兄弟或姐妹也会有差异。这种亲代与后代以及后代不同个体之间在性状上表现出来的差异,就是生物的变异。变异是生物的基本属性之一。生物为什么在一定的遗传背景下产生变异呢?原来,决定生物体性状表现的基因型不完全相同。即使基因型相同的个体,由于所处的外界环境不同,其表现型也不会完全相同。况且生物的遗传基础不是永远不变的,常常由于某种原因如: “Mother ten children, ten different tenons” is a common biological phenomenon. The essence of this phenomenon is that there are differences in the performance of traits between parents and offspring and between different individuals. The children of the same parents have similarities and differences in appearance, personality and temper, but also the twins or sisters with identical twins. This kind of difference between the parents and offspring as well as the different individuals in the offspring is the biological variation. Variation is one of the basic attributes of biology. Why biological organisms in a certain genetic background mutation? The original, the performance of the biological traits of the genotypes are not exactly the same. Even individuals with the same genotype will not have identical phenotypes because of the different external environment. Moreover, the biological basis of the genetic is not always the same, often due to some reason, such as: