Now the next question is how exactly do we pass down these blood groups from one individual to our offspring? So basically, each parent has the ability to donate a gene for that particular blood group that they actually have. So let's suppose this is the male parent chromosome, this is the female parent chromosome and this is chromosome nine for each case because this is the alley, the gene section that codes for a particular type of blood group. So this is the blood type alley. Now as we mentioned earlier, the Abo blood group locus is located on the chromosome number nine. And each allele is passed down from each one of the two parents.