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Why does hemophilia usually affect males who inherit the trait from their mothers?
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blood disease
Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.
Hemophilia is a sex-linked recessive disorder caused by a mutation in a gene located on the X chromosome.123
The reason it predominantly affects males is due to the difference in sex chromosome composition between males and females:
- Genetic Structure: Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).24
- Lack of Counterpart: The Y chromosome is much smaller than the X and lacks the corresponding genes to counteract a recessive mutation found on the X chromosome.52
- Expression: Because a male has only one X chromosome, he will express the hemophilia trait if he inherits the mutated gene from his mother. In contrast, a female would typically need to inherit the recessive allele on both of her X chromosomes to fully display the disorder; if she carries it on only one, she is generally an unaffected carrier.23
Consequently, sons inherit their single X chromosome from their mothers, making them hemizygous for any genes located on that chromosome. If that X chromosome carries the mutation for hemophilia, the son will manifest the disease.53416