（4）或者你直接进入NCBI的主页 http://www.ncbi.nlm.nih.gov/，直接搜索NAT2，出现下图中的界面，选择SNP，然后有相关SNP记录476条，点击进入后，选择HUMAN 279条，然后再逐个观察。

http://www.biomart.cn/upload/asset/2008/07/22/1216476621.gif

2、但是，从整个基因组的SNP分布和NAT2基因的位置关系上直观的工具，Genbank并不是很理想的，推荐配合Genewindow结合使用，Genewindow是很好的动态平台，十分直观，可以清晰的显示SNP的分布情况和基因内含子、外显子、调控区的关系，可以用于整体选择时使用，个人使用后感觉效果非常满意。

Genewindow的进入方法：http://genewindow.nci.nih.gov/，推荐大家使用！使用前需要安装一个插件，然后后续的界面十分友好。

1，如果是检测基因的所有已知的SNP，那么首先要去了解并查询到这些SNP位点，SNP位点可以通过查询dbSNP数据库（http://www.ncbi.nlm.nih.gov/SNP/）和TSC（The SNP Consortium）数据库（http://snp.cshl.org/），可以获知基因及上下游邻近序列的SNP位点。

2，至于挑选的原则，可以介绍一下Hap Map的正规化标准：

SNP Selection Criteria

Category 1 "verified"

This contains all SNPs for which we have allele frequency or genotyping data. This includes SNPs from the TSC allele frequency project, as well as SNPs characterized by JSNP. These SNPs were generated from those rs clusters in which at least one of the SNPs in the cluster contains genotype or allele frequency data and the minor allele must have been seen in at least two individuals.

Category 2 "two-hit"

These are true double-hit SNPs, produced in collaboration with Jim Mullikin and Sarah Hunt. A double-hit SNP must be seen twice, in two different DNA samples which must have produced two alleles. TSC trace data was only allowed to contribute one hit per allele because the individual source DNA for a trace could not be identified.

Category 3 "jsnp-verified/perlegen-verified"

This category contains two groups: SNPs that JSNP certifies are likely to be real based on manual inspection of their data (but have not been genotyped)， and SNPs that Perlegen verified independently.

Category 4 "bac-overlap"

These are SNPs from BAC overlaps that do not fall into category 1 or 2 above.

一个水稻SNP数据库: