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Where can I find a list of SNP rs IDs that belong to the X chromosome?
I'm trying to exclude the SNPs on X-chromosome in a data set, but I don't know where these SNPs come from.
I tried to use dbSNP to search, it returns 26933249 SNPs, but the webpage seems to refuse me to download the information.
You just searched for X[Chromosome], you didn't specify a species. Presumably, your dataset comes from a specific species, so you should limit your search to that species. For instance, for human, you can search dbSNP for X[Chromosome] human[organism]. Then, click on the send to link at the top left and download the data:
This is veeeeeery slow, however. I suggest that you instead download the data for chrX from dbSNP's FTP site (this assumes your species of interest is human): ftp://ftp.ncbi.nih.gov/snp/organisms/human_9606/chr_rpts/chr_X.txt.gz
Once you have this file, you can use it to filter your dataset:
Collect all rsIDs from the file:
zcat chr_X.txt.gz | awk '/^[0-9]/{print "rs"$1}' > chrX.rsIDs
Filter your dataset.
You haven't shown the format of your dataset, so if it is just a list of rsIDs like this:
$ cat dataset
rs77669712
rs199706910
rs2799940
rs12205639
rs10958205
rs200778574
You can remove any that are on chrX with:
$ grep -vxFf chrX.rsIDs dataset
rs77669712
rs199706910
rs12205639
rs10958205
rs200778574
That will print all rsIDs from the text file dataset that are not also in the text file chrX.rsIDs. Note the -x option for grep which tells it to only consider matches that cover the entire line. This ensures that rs1234 is not removed when you're looking for rs123.
