 Hello everyone and welcome to our lecture on human pedigrees. If you've ever put together a family tree, in a sense you've put together a pedigree. The purpose of a pedigree is to show who's related to who. In genetics this can go one step further and you can use a pedigree to show how genetic diseases are inherited from one generation to the next. Today we're going to be focusing on a famous example of a genetic disease known as hemophilia. Hemophilia is a blood disease and those who exhibit this disease have blood that is unable to clot. So something like a simple scratch, a simple cut, or even a small bruise can be lethal. Hemophilia is also known as the royal disease because it was carried throughout Queen Victoria of England's bloodline. In fact through her bloodline this disease was spread to Russia, Germany and even Spain. Now in a human pedigree, squares are used to represent men and circles are used to represent women. Those who actually exhibit a disease will have either their square or their circle completely filled in. Those who are known as being carriers, meaning they don't exhibit the disease but they do have one copy of the gene for it, will be shown with half of their circle or their square filled in. Queen Victoria was known as being a carrier of hemophilia. She married Prince Albert and through their marriage, as you can see, they had one, two, three, four, five girls and then they had one, two, three, four boys and of the boys, one Leopold was a hemophiliac. He exhibited the disease of hemophilia. Now of the girls Alice was known to be a carrier of the disease. The reason we know this is because when she was married she had one, two, three, four, five girls and she had one, two boys and of her boys, one of them was a hemophiliac. Of the girls, Alexandra who would marry the Tsar of Russia was a carrier and she had one, two, three, four girls and one boy with her husband. Interestingly, there was a lot of pressure at the time for her to give birth to a boy and it was a real worry for their family when they found out that their son, whose name was Alexi, had hemophilia. If people had known that she had given a son who had hemophilia the public would have become upset because there would have been no one to inherit the royal crown. Unfortunately then Alexandra and her husband decided to hide the fact that their son had hemophilia so they became withdrawn from the public. Eventually this led to the public becoming very discontent with their leadership because many of the people were suffering in poor and eventually there was a Russian revolution. Unfortunately for the family Alexandra, her husband and all of their children were executed all because they became withdrawn and were trying to actually hide the fact that their son had hemophilia. Now Alice's other child Irene was also found to be a carrier and she married into German royalty. She and her husband had three boys and fortunately two of the three were hemophiliacs. So far Queen Victoria's blood disease has gone through Russia and now Germany. Now, Leopold did live long enough to get married and have children. One of his children, Alice, was found to be a carrier because when she became married to her husband they had one girl and two boys and one of the boys was a hemophiliac. Lastly, Beatrice was also a carrier. We know this because when she became married she had one girl and one, two, three boys. Of them two of the three boys were hemophiliacs and later on it was discovered that the girl was a carrier. The girl's name was Victoria and she married into Spanish royalty. She and her husband had one, two, three, four, five boys two of which were hemophiliacs. Now, she also had one, two girls and none of their children happened to have hemophilia. As you can see Queen Victoria's genetic disease which started out in England spread to Russia, Germany, and Spain. Pretty interesting how a story like this can actually lead to a Russian revolution, isn't it?