2013考研英语二图表作文预测:出生率和婴儿死亡率

采用了恰当的衔接手法，层次清晰；作者句法很棒，合理使用了复杂句；作者学术词汇使用比较准确，词汇表达较丰富，但仍需增加词汇积累；请提高文章内敛性，段落和句子要围绕主题展开；请注意分段。

　　The ligation and transformation are two crucial steps during the construction of BAC library. The final recovered LMP agarose gel blocks embedding DNA should be eluted to recover DNA in dialytic-bag by PFGE before ligation, the elution solution dissolving DNA was then directly used as ligation system, so the concentration and purity of DNA dissolved in the elution solution are crucial for next ligation reaction. To satisfy these needs, the electrophoresis buffer must be prepared with sterilized ultrapure water, the eluted DNA should be quantitatively analyzed to satisfy the optimal ratio between DNA and BAC vector, and the DNA should be ligated with the BAC vector immediately. For increasing the transformation efficiency, the DNA ligase should be inactivated at 65°C after the ligation reaction was finished, the ligation product need to be desalted by dialysis, and transformed immediately.