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In The Pedigree Below, The Shaded Symbols Indicate People Who Have Hemophilia. Which Mothers Certainly Are Carriers? Why Did The Sons Of Person 3 Not Inherit The Trait?

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aileeny answered
Which pedigree below?  I cannot see it and neither can anyone else!!   But what I can tell you is that Haemophilia is a sex-linked inheritance pattern carried on the x chromosome.  Because women have two x chromosomes then a mother carrier ( person 3??)   will have the normal dominant x and the mutated x and she has a 50/50 chance with each conception of passing on either one to all her sons or daughters. If she passes on the "bad" x to a daughter ,who will also receive a normal x from her father ( unless of course he is a haemophiliac) then the said daughter will be a carrier but if the mother carrier passes the "bad" x to her son then he will become a haemophiliac as he will only receive a y chromosome from dad and so the mutated haemophiliac gene./allele will act as a dominant.   So a carrier mum and a normal dad ( refer haemophilia) can have normal sons and daughters but also carrier daughters and haemophiliac sons. If you take a look at a haemophiliac family pedigree you will be able to trace this.  Please tell me if this helps!!

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