In my last post I explained why mutations rarely make a difference in our lives, so it is only fitting that I dedicate this post to a mutation that has changed, and is still changing, the lives of billions of people. The learned reader may be wondering why this is newsworthy – aren’t mutations constantly changing lives by driving evolution? Of course, but this is the story of how one minor mutation changed the world without influencing evolution.
Our story begins with none other than Queen Victoria, who had nine children despite abhorring pregnancy and finding babies ugly. Once they were grown and presumably better-looking, Victoria arranged for her children and grandchildren to marry into various royal families, effectively uniting them into one big European royal family. This might have been good for preventing wars (temporarily, at least) but it also resulted in a clotting disorder spreading throughout the royal bloodlines because unbeknownst to Victoria, she was a carrier of Hemophilia B.
We now know that Hemophilia B is caused by a mutation in a gene that encodes a clotting protein known as factor IX. As a result of this mutation, no functional factor IX is produced, and excessive hemorrhaging can ensue. Queen Victoria herself was blissfully unaware of this problem because the gene that encodes factor IX is located on the X chromosome. Females have two X chromosomes in each of their cells, whereas males only have one. This means that females have two copies of the factor IX gene, and if one copy is mutated, the other copy can make up for it by producing functional factor IX proteins. Males, on the other hand, only have one copy of the factor IX gene, and if that copy happens to be mutated, they will suffer from Hemophilia B. Consequently, males are more commonly afflicted with Hemophilia B, while females like Queen Victoria are carriers of the disorder who can pass it on to their sons without personally suffering from it.
Victoria passed her mutant factor IX gene on to three of her children, including her daughter Alice, who in turn passed it on to her daughter Alix. Alix married Tsar Nicholas of Russia and bore him four daughters. While this might sound wonderful to modern ears, her apparent inability to produce a male heir was cause for great concern in the imperial court and contributed to her unpopularity. So when she finally gave birth to a son in 1904, the Tsar and Tsarina thought they were out of the woods – until little Alexei’s umbilical cord was cut and his navel bled for hours. Terrified that the news of Alexei’s hemophilia, which could render the most minor injury fatal, would endanger both Alexei and their family’s future, the Tsar and Tsarina kept their son’s disease a state secret. They became entangled with a faith healer and mystic who claimed he could cure Alexei and made some disastrous political mistakes at his advice. Consequently, the Russian Revolution broke out, resulting in the abolition of the monarchy and the establishment of the Soviet Union, the first communist state in the world. In other words, a single mutation on a little boy’s X chromosome brought about a revolution that changed the world forever and still reverberates today in countries like China and Cuba.
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