罗登元 2016-11-28 07:54
<p> <span></span><span><span style="font-family:宋体;">一、因为</span><span><span>R</span></span><span style="font-family:宋体;">型与</span><span><span>S</span></span><span style="font-family:宋体;">型的</span><span><span>DNA</span></span><span style="font-family:宋体;">可以同源区段配对，形成杂合细菌，通过分裂生殖形成</span><span><span>R</span></span><span style="font-family:宋体;">型和</span><span><span>S</span></span><span style="font-family:宋体;">型两种后代，不象许多人认为的（</span><span><span>R</span></span><span style="font-family:宋体;">型直接变成</span><span><span>S</span></span><span style="font-family:宋体;">型）；</span></span> </p> <p> <span></span><span><span style="font-family:宋体;">二、无荚膜的</span><span><span>R</span></span><span style="font-family:宋体;">型有非常重要的感受态，保证了</span><span><span>S</span></span><span style="font-family:宋体;">型的</span><span><span>DNA</span></span><span style="font-family:宋体;">可以进入。反之则不会发生：</span><span><span>S</span></span><span style="font-family:宋体;">型有荚膜，无感受态，不能作为受体菌，若人为除去荚膜，培养出无荚膜的后代，它就同时丧失了毒性，变成</span><span><span>R</span></span><span style="font-family:宋体;">型，当然就会有了感受态。</span></span> </p>