This is an absolutely incredible story! An 11-year-old Czech girl was found to have inherited almost all of her genetic makeup from her dad, and virtually none from her mom. Usually, a child is made up of half of each parent's genes. But in very rare cases, a child will inherit the majority of their genes from one parent. It's an actual genetic syndrome, and this little girl is one of only 25 people in the entire world known to have it. What's even crazier: all of them are girls!
This genetic syndrome is known as an imprinted gene disorder. Basically, it's a condition in which at least one gene is doubled up from mom or dad. Even 10 years ago, geneticists believed that this condition was incompatible with life. In fact, the Czech girl appears to be the only person who has the disorder who has not developed cancer. It's incredibly rare, although more and more cases are being discovered thanks to improved genetic testing around the world.
In the case of the Czech girl, her parents wanted to find out why she was deaf. After undergoing genetic testing when she was nine years old, doctors discovered that she had two identical copies of a rare gene. Initially, they believed it to be a case of extremely bad luck, inheriting the same gene from each parent. But further testing revealed that her mother was a carrier of this particular gene. In other words, she inherited BOTH copies of the gene from her father.
But it wasn't just that one gene. She had, in fact, doubled up on her father's genes in nearly all of her chromosomes and in most of her cells! But the girl and her father aren't twins (identical twins split an egg and end up with almost uniform genetic makeups). This is what's known as a genetic mosaic, because there is some variation in different tissues. 74% of the cells in her saliva showed only paternal genes, while only 7% of the cells in her blood showed maternal genes.
For most of the other 25 cases in the world, this doubling up of paternal genes has resulted in cancer. But so far, this amazing 11-year-old girl has avoided that fate. Incredibly, doctors still aren't sure if her deafness was caused by the double dad genes. The gene they initially suspected to be the cause is found doubled up in about 1 in 50 Europeans, with no discernible health issue related to it.