Talk:Emilio Fuller/@comment-44475519-20191201214312/@comment-33165213-20191202114537

Maybe Marconi has cis AB blood type, a rare type of mutation in the blood gene, where one allele is identified as AB, while the other allele is identified as O.

Coincidentally, Emilio's mother probably has normal O blood type and somehow Emilio got the the allele from both parents, resulting he has O blood type.

Still confused, this article might explain this.

https://genetics.thetech.org/ask-a-geneticist/cis-ab