经过两个月的学习,《遗传和变异》这章已近尾声。如何突破遗传题,是困扰学生的重要问题。下面就遗传题的突破方法例析如下,以供同学们参考。例1.人类的皮肤含有黑色素,黑人含量最多,白人含量最少。皮肤中黑色素的多少,由两对独立遗传的基因(A和a,B和b)所控制;显性基因A和B可以使黑色素量增加,两者增加的量相等,并且可以累加。若一纯种黑人和 After two months of study, the chapter “Genetics and Variation” is almost over. How to break through the genetic problem is an important problem plaguing students. Here's a breakthrough on the genetic problem analysis as follows, for the students reference. Example 1. Human skin contains melanin, black most, white least. The amount of melanin in the skin is governed by two independently inherited genes (A and a, B and b); the dominant genes A and B increase the amount of melanin, both increasing in equal amounts and accumulating. If a purebred black and