“DNA 的粗提取与鉴定”实验是中学生物教学中的重点实验,在实际教学中我们做了一些改进,取得了不错的效果。一、实验材料的选择课本推荐使用的实验材料是鸡血,优点是细胞易破裂,DNA 含量大,现象明显;缺点一是费用太高,对普通学校来说,买活鸡显然不现实,与市场上的小商贩联系购买新鲜鸡血,很难定时、定量地保证供应;二是实验步骤烦琐,操作要求高,学生一堂课很难完成实验。而选用植物组织最大的好处是取材简便,极大地降低了费用,而且在实验过程中能始终保持清洁,我们试过多种实验材料,其中菜花由于含水量少,细胞破裂情况及 DNA 溶出的量都不如洋葱效果好,最终我们选择了洋葱。 The “Rough Extraction and Identification of DNA” experiment is a key experiment in biology teaching in middle schools. We have made some improvements in actual teaching and achieved good results. First, the choice of experimental materials Experimental materials recommended for textbooks are chicken blood, the advantage is that cells are easy to rupture, DNA content is large, the phenomenon is obvious; the first is that the cost is too high, for ordinary schools, buying live chicken is obviously unrealistic, and Small traders on the market contact with fresh chicken blood, it is difficult to ensure the supply of regular, quantitative, and second, the experimental procedures are cumbersome, high operating requirements, students can not complete the experiment in one lesson. The greatest advantage of choosing a plant tissue is that it is easy to draw, greatly reduces the cost, and it is always kept clean during the experiment. We have tried a variety of experimental materials, including cauliflower because of low water content, cell rupture and the amount of DNA elution. Not as good as the onion, we eventually chose onions.