SAO flag in dpsnp

Question

[Rna-Seq]

Hi

I would like to ask about the meaning of unspecified of SAO flag in dpsnp files

In addition, when I downloaded rat dbsnp files, I found that all snaps have SAO=0 (unspecified). Any idea?

dpsnp vcf files for rat has SAO which is defined as follows:

##INFO=<ID=SAO,Number=1,Type=Integer,Description="Variant Allele Origin: 0 - unspecified, 1 - Germline, 2 - Somatic, 3 - Both">

Any help is appreciated. Thank you