The best evidence would be two of her sons having hemophilia while one does not.
<h3>Hemophilia</h3>
Hemophilia is a sex-linked recessive disorder. This means that females can be homzygous normal, heterozygous, or affected by the disorder while males can either be normal or affected.
Why? This is because males have only one X chromosome (XY) while females have 2 X chromosomes (XX).
Also, the X chromosomes in males are always from their mothers while their Y chromosomes come from the father.
So, if the two X chromosomes of Irene are normal for hemophilia, none of her sons should be affected. If the two X chromosomes are affected, all her sons will have the disorders.
When one X chromosome is affected and the other is normal, it means that some of her sons will inherit the affected chromosome and have the disorder while some will inherit the normal chromosome and will be free from hemophilia.
More on hemophilia can be found here: brainly.com/question/18916729
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