<p>For a study I need some kind of &quot;decoy&quot; GWAS-data. For this I created a panel with some genes, the same ones as in the real data. From NCBI I fetch some of their SNPs and create my own artificial .ped and .map file. Furthermore I save for each snp if it lies on the X-Chromosome.</p>
<p>I then go on and randomly create female individuals by giving them heterozygous alleles on their X-Chromosome genes. Males only get homozygous ones.</p>
<p>But when I then run pLink with the <code>--check-sex</code> argument I get a sexcheck file where there's only zeroes in the <code>SNPSEX</code> column. So do you know how <code>--check-sex</code> works that I can then create decoy-individuals that reliably (as much as possible) get detected as a given gender?</p>

CC BY-SA 4.0
2021-02-18T12:42:16.530Z
I was able to create a sample map/ped files that result in SNPSEX column being populated in plink 1.19 using 1000genomes Xchrom - found in their FAQ: https://www.internationalgenome.org/faq/where-are-snps-xymitochondrial-chr/. 

The relevant conversion command `./plink  --check-sex --vcf ../ALL.chrX.phase3_shapeit2_mvncall_integrated_v1b.20130502.genotypes.vcf --maf 0.05 --out ped_map_chrX/chrmX --recode` .

Even in this dataset, SNPSEX is 0 (ambiguous) in 400 (~16%) of cases. One could start pruning from here to arrive at a suitable minimal set of SNPs that are still recognised in plink.
ellimilial
CC BY-SA 4.0
2021-02-19T10:03:39.490Z
Ok, thanks! I'll try that out.
Cowboy_Patrick
<python><plink>
Reliably create female and male individuals in a -ped file for plink
# Reliably create female and male individuals in a -ped file for plink

(Asked by: username_0 on 2021-02-17)

For a study I need some kind of "decoy" GWAS-data. For this I created a panel with some genes, the same ones as in the real data. From NCBI I fetch some of their SNPs and create my own artificial .ped and .map file. Furthermore I save for each snp if it lies on the X-Chromosome.

I then go on and randomly create female individuals by giving them heterozygous alleles on their X-Chromosome genes. Males only get homozygous ones.

But when I then run pLink with the `--check-sex` argument I get a sexcheck file where there's only zeroes in the `SNPSEX` column. So do you know how `--check-sex` works that I can then create decoy-individuals that reliably (as much as possible) get detected as a given gender?

**Tags:** python, plink
> **Comments:**
> **username_1**: I was able to create a sample map/ped files that result in SNPSEX column being populated in plink 1.19 using 1000genomes Xchrom - found in their FAQ: https://www.internationalgenome.org/faq/where-are-snps-xymitochondrial-chr/.   The relevant conversion command `./plink  --check-sex --vcf ../ALL.chrX.phase3_shapeit2_mvncall_integrated_v1b.20130502.genotypes.vcf --maf 0.05 --out ped_map_chrX/chrmX --recode` .  Even in this dataset, SNPSEX is 0 (ambiguous) in 400 (~16%) of cases. One could start pruning from here to arrive at a suitable minimal set of SNPs that are still recognised in plink.  
> **username_0**: Ok, thanks! I'll try that out.  

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## 0 answers

