题目

阅读理解 How far would you go for your kids education? That's aquestion many parents are asking in the wake of the college cheating scandal(丑闻)involving 38 wealthy parents aroundthe country, including actresses Lori Loughlin and Felicity Huffman.Here's how far I went. In the fall of 2017 my husband and I lost our jobs. Wehad to tell our daughter, Casey, that we couldn't afford to send her back toschool for her junior year at Fordham University. We decided the best choicefor our family would be for Casey to sit out a year. We promised that we wouldget her back the following year. Casey 噬菌体侵染细菌的实验过程，证明了噬菌体前后代性状的传递是靠DNA完成的。请根据实验内容回答如下问题。 (1)用32P标记的一个噬菌体侵染大肠杆菌，待细菌解体后，检测到有256个噬菌体放出，则所释放出的噬菌体中，含32P的噬菌体与含31P的噬菌体的比例为______，在此实验之前，怎样才能使噬菌体的DNA标记上32P？________________________。 (2)32P标记的噬菌体侵染大肠杆菌，在理论上，上清液中不含放射性，下层沉淀中具有很高的放射性。由于实验数据和理论数据之间有较大的差异，请对实验过程进行误差分析。 ①在实验中，从噬菌体和大肠杆菌混合培养，到搅拌并用离心机分离这一段时间如果过长，会使上清液的放射性含量______，其原因是______________________。 ②在实验中，如果有一部分噬菌体没有侵染到大肠杆菌细胞内，是否是误差的来源？______。请简述理由：__________________________________________________。