题目

基因型分别为AaBbCCDd和AABbCCdd的两种豌豆杂交，其子代中纯合体的比例为A. 0 B. 1/4 C. 1/8 D. 1/16 答案：【答案】C【解析】自由组合定律的实质：位于非同源染色体上的非等位基因的分离或组合是互不干扰的。在减数分裂形成配子的过程中，同源染色体上的等位基因彼此分离，非同源染色体上的非等位基因自由组合。基因型分别为AaBbCCDd和AABbCCdd的两种豌豆杂交，可以分解成Aa×AA、Bb×Bb、CC×CC、Dd×dd四个I have two friends.        names are Lucy and Lily. They are twins（双胞胎）. They        from the USA.Lucy and Lily look the same.        have blue eyes and brown hair. They are thirteen      old. But they are in different clothes. Red is        favorite color. She is often（经常）in red. But this morning,        coat is yellow and her pants        blue and she has brown shoes. Lily likes green. This morning she is        a green skirt and her shoes are green, too.They often help me with my English.        are in the same grade, but in different       .小题1:A．Their               B．They                 C．Theirs小题2:A．comes               B．come                C．is小题3:A．They’re            B．They                 C．Their小题4:A．year                B．year’s              C．years小题5:A．Lucy’s             B．Lucy                 C．Lucys’小题6:A．she             B．he                   C．her小题7:A．are             B．is                   C．be小题8:A．at                  B．from                 C．in小题9:A．Our             B．We                   C．Us小题10:A．class              B．classes              C．Grade