Question

Hemophilia is a hereditary bleeding disorder that primarily affects males. In 3–5 sentences, summarize why this condition typically affects males more than females.A chart shows the British hemophilia line. ▼Click for Long DescThe chart shows Queen Victoria with an unaffected X chromosome and an affected X chromosome and Albert of Saxe Coburg Gotha with an unaffected X chromosome and a Y chromosome at the top. Their children in the second generation are as follows. Victoria with two unaffected X chromosomes. King Edward the seventh with an unaffected X chromosome and a Y chromosome. Alice with an unaffected X chromosome and an affected X chromosome. Alfred with an unaffected X chromosome and a Y chromosome. Helena with two unaffected X chromosomes; a question mark is placed next to the chromosomes. Louise with two unaffected X chromosomes, a question mark is placed next to the chromosomes. Arthur with an unaffected X chromosome and a Y chromosome. Leopold with an affected X chromosome and a Y chromosome. Beatrice with an unaffected X chromosome and an affected X chromosome. Alice with Grand Duke Louis fourth of Hesse (an unaffected X chromosome and a Y chromosome) had the following children in the third generation. Victoria with two unaffected X chromosomes. Elisabeth with two unaffected X chromosomes. Irene with an unaffected X chromosome and an affected X chromosome. Grand Duke Ernest Louis with an unaffected X chromosome and a Y chromosome. Frederick with an affected X chromosome and a Y chromosome. Alix with an unaffected X chromosome and an affected X chromosome. Irene and Henry of Prussia (an unaffected X chromosome and a Y chromosome) had the following children in the fourth generation. Waldemar with an affected X chromosome and a Y chromosome. Sigismund with an unaffected X chromosome and a Y chromosome. Henry with an affected X chromosome and a Y chromosome. Alix and Emperor Nicholas second of Russia (an unaffected X chromosome and a Y chromosome) had the following children in the fourth generation. Olga with two unaffected X chromosomes; a question mark is placed next to the chromosomes. Tatiana with two unaffected X chromosomes; a question mark is placed next to the chromosomes. Marie with two unaffected X chromosomes; a question mark is placed next to the chromosomes. Anastasia with two unaffected X chromosomes; a question mark is placed next to the chromosomes. Alexei with an affected X chromosome and a Y chromosome. Leopold and Helen of Waldeck (two unaffected X chromosomes) from the second generation had only daughter with an unaffected X chromosome and an affected X chromosome. Alix with Alexander Cambridge first Earl of Athlone (an unaffected X chromosome and a Y chromosome) had the following children in the fourth generation. May with two unaffected X chromosomes. Rupert with an affected X chromosome and a Y chromosome. Maurice with an affected X chromosome and a Y chromosome. Beatrice and Henry of Battenberg (an unaffected X chromosome and a Y chromosome) from the second generation had the following children in the third generation. Alexander Mountbatten first Marquess of Carisbrooke with an unaffected X chromosome and a Y chromosome. Victoria Eugenie with an unaffected X chromosome and an affected X chromosome. Leopold with an affected X chromosome and a Y chromosome. Maurice with an affected X chromosome and a Y chromosome; a question mark is placed next to the chromosomes. Victoria Eugenie and King Alfonso thirteenth of Spain (an unaffected X chromosome and a Y chromosome) from the third generation had the following children in the fourth generation. Alfonso with an affected X chromosome and a Y chromosome. Jaime with an unaffected X chromosome and a Y chromosome. Cristina with two unaffected X chromosomes. Gonzalo with an affected X chromosome and a Y chromosome.

Answer 1

Hemophilia is usually X‑linked recessive: the genes for the common forms (factor VIII in hemophilia A, factor IX in hemophilia B) are on the X chromosome. Males (XY) have only one X, so a single mutated allele on their X causes disease. Females (XX) normally need mutations on both X chromosomes to be affected, so they are usually asymptomatic carriers who can pass the mutated X to their sons. Rarely, X‑inactivation skewing or two mutated Xs can make a female affected.