blt 0 Posted April 19, 2017 Why hemophilia is lethal (in almost 100%) for homozygotic females, while it's not lethal for hemizygotic males? Both, homozygotic females and hemizygotic males don't have any healthy allel. Thank you for replies 0 Share this post Link to post Share on other sites
Daecon 192 Posted April 19, 2017 (edited) At what stage of development does the lethality usually occur in females? Edited April 19, 2017 by Daecon 0 Share this post Link to post Share on other sites
blt 0 Posted April 19, 2017 In prenatal stage, as I heard. 0 Share this post Link to post Share on other sites
John Cuthber 3813 Posted April 19, 2017 How often does anyone find out?As far as I can see you would need a haemophiliac father and a carrier mother. That's a fairly rare combination. Also, until fairly recently, there was a good chance that the "father" didn't survive until adulthood. 0 Share this post Link to post Share on other sites
blt 0 Posted April 20, 2017 I know it is very rare situation. But what is the genetic reason of lethality of XhXh? If mutation changes life-important gene at X chromosome, then XhY- should also be lethal. But it isn't. Many males live quite normally, and some of them even don't know they are sick. It's easy to understand why some mutations on X chromosome are lethal for males and aren't for females. Females have second X chromosome where healthy gene exists. This rescues females lives in many recesive X-linked diseases. But hemophilia is also recesive X-linked disease and situation is opposite. It's often not lethal for hemizygotic males (XhY-), where there is no chance for healthy gene, because there is no second X chromosome. It's lethal for homozygotic females (XhXh), where there is also no chance for healthy gene. Why it is like that? 0 Share this post Link to post Share on other sites
Daecon 192 Posted April 20, 2017 I guess the Y chromosome is dominant and so overpowers any haemophilia effect on the X chromosome? 0 Share this post Link to post Share on other sites
blt 0 Posted April 20, 2017 The gene is on X chromosome, not on Y chromosome, so it can't be the reason. 0 Share this post Link to post Share on other sites
John S 0 Posted September 17, 2017 Here's a report on an adult female who was homozygous for hemophilia: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385172/. She suffered from the condition as expected, but it was not lethal. And here's the abstract of another report of a homozygous adult female who had the condition but for whom it was not lethal: https://www.karger.com/Article/PDF/208614. 0 Share this post Link to post Share on other sites
jimmydasaint 176 Posted September 17, 2017 (edited) IIRC, there are about 13 factors for clotting to occur perfectly. Heterozygotic males, namely XhY, have little Factor VIII or IX but DO have platelets to aid clotting . So, if I am correct, some clotting still occurs although it is imperfect. Edited September 17, 2017 by jimmydasaint 0 Share this post Link to post Share on other sites