If one X chromosome is healthy and one is mutated, why does the healthy take control?
In: 8
The X chromosome has genes for all kinds of things, including things that you wouldn’t think were related to sex.
You might know that Queen Victoria was a hemophilia carrier. The gene that tells the body how to make the stuff that gets your blood to clot is on the X chromosome. If you have at least one copy of that gene, your body can make that stuff, and you don’t have hemophilia.
Queen Victoria had two X chromosomes, one with a normal copy of the gene, one with a mutated copy, so she didn’t have hemophilia. When her egg cells formed, they got one of her two X chromosomes. Any of her daughters would have gotten another X chromosome as well, from Albert. They might get a normal or defective X chromosome from her, but they also had a normal one from him,so they didn’t have hemophilia. Her sons got one X chromosome from her and a Y chromosome from him. They had a 50% chance of getting the good X chromosome, and a 50% chance of getting the bad one. If they inherited her defective X chromosome, they didn’t have a backup copy of the gene, so their bodies couldn’t produce the stuff that gets blood to clot.
Victoria’s daughter Alexandra got the bad X chromosome from her mother, then passed it on to her son, the Tsarevich Alexei of Russia, who had hemophilia. Then Rasputin claimed to be able to help Alexei. He gained Alexandra’s trust, which was unpopular with the Russian people, and it was a factor in the revolution.
Note: this applies to organisms that use the XY system of determining sex. There are other systems as well. Birds use the ZW system, where male birds get two Z chromosomes and females get one Z and one W. In those species, the females would be more likely to get genetic disorders than the males.
Latest Answers