1，如果是檢測基因的所有已知的SNP，那么首先要去了解并查詢到這些SNP位點，SNP位點可以通過查詢dbSNP數據庫（http://www.ncbi.nlm.nih.gov/SNP/）和TSC（The SNP Consortium）數據庫（http://snp.cshl.org/），可以獲知基因及上下游鄰近序列的SNP位點。
2，至于挑選的原則，可以介紹一下Hap Map的正規化標準：
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 inpiduals.
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
inpidual 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.