RNA的制备与分析对于了解基因在转录水平上的表达与调控和cDNA的合成都是必须的，RNA的纯度和完整性对于Northern blot，RT-PCR和cDNA文库的构建等分子生物学实验都至关重要。RNA分离的方法很多，其中最关键的因素是尽量减少RNA酶的污染

实验目的：学习RNA的简易制备过程，通过RNA电泳带评价RNA质量

实验材料：水稻幼嫩叶片

实验原理：SDS是一种去污剂，可以抑制内源RNA酶的活性，它不但可解聚核酸与蛋白质的结合，还可与蛋白质带正电荷的侧链结合，形成SDS－蛋白质复合物而沉淀。4 M LiCl可选择性沉淀RNA。

实验步骤：

1.      Harvest fresh leaf discs in 2 ml eppendorf tubes and freeze quickly in liquid nitrogen and store at -80ºC until use.

2.      Grind leaf discs using a steel bar (precooled in liquid nitrogen) that perfectly fits the eppendorf tube. Keep the plant material frozen allows easy grinding to a fine powder.

3.      After grinding , add 500ml of hot extraction buffer (80℃) and phenol (1:1 ) (250 ml of each). (Extraction buffer: 0.1 M  LiCl, 100 mM Tris.HCl pH=8.0, 10 mM EDTA, 1% SDS)

4.Homogenized the mixtures by vortex for 30 seconds, and add 250 ml chloroform/isoamylalcohol (24:1) and vortex.

5.Centrifuge for 5 min, remove the waterphases and mix with one volume of 4 M LiCl.

6.Store RNAs at 4℃ overnight and centrifuge for 10 min.

7.Dissolve the pellets in 250 ml DEPC water, add 0.1 vol. of 3 M NaOAc (pH 5.2), and precipitate the RNAs with 2.5 vols of ethanol.

8.Centrifuge for 10 min for 4℃, wash the RNA pellets with 70% EtOH and dry the pellets.

9.Dissolve the pellets in 15 ml DEPC water.

(Routinely between 25 and 50 mg of total RNA is obtained from 100 mg tobacco, tomato or potato leaf tissue)