题目内容

对两个基因的噬菌体杂交所测定的重组频率如下：试问:（1）a、b、c 3个突变在连锁图上的次序如何？为什么它们之间的距离不是累加的？（2）假定三因子杂交，ab+c×a+bc+，你预期哪种类型的重组体频率最低？（3）计算从 ⑵ 所假定的三因子杂交中出现的各种重组类型的频率。

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Hfr met+ thi+ pur+×F- met- thi- pur-杂交。中断杂交试验表明，met+最后进入受体。所以只在含thi和pur的培养基上选择met+接合后重组体。检验这些接合后体存在的thi+和pur+，发现各基因型个体数如下：试问：（1）选择培养基中为什么不考虑met?（2）基因次序是什么？（3）重组单位的图距有多大？（4）这里为什么不出现基因型met+ thi+ pur-的个体？

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Find out the points of benefits of walking in the following paragraph 4.Walking is the best exercise for physical health. The impact of weight on your limbs and joints will strength with older people, it’s never too late to build up bone density. It increases circulation and makes your metabolism work faster. This means you’ll burn more calories, and the nutrients from food will be absorbed by your body in a more efficient way. This will encourage you to drink more water, which will improve digestion and clean your system. Among many benefits is the glow of good health. Walking is also good for protection against heart disease and can lower cholesterol.

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