The idea for the mother’s curse goes like this. Most human genes are on chromosomes, but a tiny number are in mitochondria, little power factories in human cells that for reasons of evolutionary history have their own loops of DNA. Sperm do not pass on any mitochondria, but eggs do. Therefore, all sons and daughters inherit their mitochondrial DNA from their mother (great mother’s day present idea: sequence yourmitochondria, make into cool figure, give it to your mom thanking her for the DNA). If a harmful mutation in mitochondrial DNA ends up in a woman, she will be less evolutionarily “fit” and thus less able to pass it along. But if the mutation ends up in a man, nothing happens. He never passes along mitochondrial DNA anyway.
However, this hasn’t been tested all that often in humans. Until a perfect system arose. You see, the first King’s Daughters—or filles du roi—arrived in New France in 1663, and 800 more would follow over the next decade. They were poor and usually of common birth, but their passage and dowry were indeed paid by King Louis XIV for the purpose of empire building: These women were to marry male colonists and have many children, thus strengthening France’s hold on North America. And so they did.
One of these is Leber’s hereditary optic neuropathy, which causes vision loss, usually in young men. Recently, geneticists using French Canadian genealogy have reexamined the effects of Leber’s and found a striking pattern of inheritance: It seems to show a long-theorized but never-seen-in-humans pattern called the “mother’s curse.”
Want to know more? Read about it here.