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例1 某育种专家在农田中发现一株大穗不抗病的小麦(控制小麦穗大与穗小的基因分别用D、d表示, 控制不抗病与抗病的基因分别用T、t表示),自花授粉后获得160粒种子,这些种子发育成的小麦中有30株为大穗抗病,有x(x≠0))株为小穗抗病,其余都染病。若将这30株大穗抗病的小麦作为亲本自交,在其F1中选择大穗抗病的再进行自交,F2中能稳定遗传的大穗抗病小麦占F2中所有大穗抗病小麦的比例为多少? 解析(1)30株大穗抗病小麦的基因型为DDtt或
Example 1 A breeding expert found a large spike-resistant wheat in farmland (the genes that control the spike size and the panicle size of wheat are denoted by D and d, respectively; the genes that control the disease resistance and disease resistance are denoted by T and t respectively. ) 160 seeds were obtained after self-pollination. 30 of the seeds developed from these seeds were resistant to large spikes, and x (x≠0)) strains were resistant to spikelets and others were infected. If these 30 wheat with large spike-resistance are self-crossed as parents, the large-spike disease-resistance in F1 is selected for self-introduction, and the large spike-resistance wheat with stable inheritance in F2 accounts for all large-spread disease resistance in F2. What is the proportion of wheat? Analysis (1) The genotype of 30 large spike-resistant wheat is DDtt or