My whole-genome sequence showed me to be heterozygous for the G to A SNP rs140578907 in the calicin gene at location 36170317 of chromosome 9, which causes an arginine to glutamine change at position 273 of the calicin protein. This SNP is very rare, the A allele having a frequency of less than 0.1%. The calicin protein is said to be an integral protein of the head of a sperm cell so I thought that perhaps the rarity of this mutation might indicate that a sperm with this mutation might not be able to fertilize an egg. If so, this mutation could only be inherited through the all-female line, like mitochondrial DNA, except that, unlike mitochondrial DNA, this mutation would only have a 50% chance of being inherited for each transmission. To determine whether I inherited this SNP from my father or mother, I had my 2 sons tested for it. Luckily, the 23andMe Relative Finder test had already shown that one of my sons and I, but not the other son, match my paternal first cousin for the region of the calicin gene. So one of my sons inherited my paternal DNA in this region and the other son inherited my maternal DNA. I just received the results of my sons' tests and, lo and behold, the son who inherited my paternal DNA is positive for this SNP and the other son is negative. This means that the SNP is on the DNA that I inherited from my father, and a sperm with the A allele managed to fertilize an egg in 2 transmission events, producing me and one of my sons. I conclude from this that this SNP has little if any effect on sperm potency. The reason for the rarity of the SNP is an open question, but perhaps it is just a relatively recent SNP. It is mostly confined to people of European extraction, which would tend to support this.