关于外周血DNA提取实验的问题！在线等。。。

1.DNA 提取中会污染任何物质 蛋白 糖类 RNA等。其纯度一般用核算吸收OD260/OD280（蛋白质污染）分析判断，纯DNA比值为1.8。此外用OD280/OD230估计盐离子是不是太高。
2.原因：鲜血中白细胞破裂的少，因此DNA降解的少。不新鲜血液一般自溶或者别的原因裂解导致DNA降解。
3.主要担心 DNA裂解酶 因此一般加入EDTA。此外一定要保存在偏碱性环境中，因为容易酸水解。别的没什么，别担心。

1. impurity of a DNA preparation is proteins or/and RNA. So， you would like to have DAN preparation with high quality and purity， you have to get rid of proteins and RNA.

2. fresh blood would make good quality of DNA. If you keep blood for long time， because it is so nutrition-rich material， bacteria may grow， that will ruin your samples. Also， DNA source in blood is from white blood cells. You would not like white cell autolysis which will lead DNA degradation， you would like to prepare DNA from fresh samples.

3. DNA should be kept at -80 centigrade degree for long storage， or -20 degree， or 4 degree for short term storage， and it should be in TE buffer. pH8.0 is good for DNA preservation. Try not use water. Therefore， low temperature， pH value around 8.0， and chelate (EDTA) are factors necessary for DNA storage.