Difference between dbsnp131, dbsnp132 and dbsnp135

[thedamian]

Hi,
I try to understand the diference betweend dbsnp131, dbsnp132 and dbsnp135.
Why there are three human polymorphism databases? For me it seems that dbsnp135 include all entries from 131 and 132. Why new databases are created, instead of extending the current ones? It's no clear enough for me.

Thx for a reply

[ymc]

I think it is for backward compatibility.

[arvid]

Well, actually they are extending each other. What you are referring to isn't actually new databases, they are new builds of a database.
A new build consists of the older known entries plus new ones (and possibly removed, incorrect entries). This is quite common (and good) practice for database maintainers. It makes life much easier in comparing analyses from older publications, given that the authors reference which build of a given database they used.