Answer:
This disorder is caused by a recessive allele, its inheritance is sex-linked.
Explanation:
The disorder affects boys born to unaffected parents, this means that at least one of them has to be a carrier of the allele which causes the disease. So, if the allele was dominant, it would express in parents and sons. But, in this case, only is expressed in sons, so it can´t be dominant. Moreover, this condition has a sex-linked inheritance because it is always seen in boys and never in girls. This happens due to boys only have an X chromosome, so if they inherit the recessive allele of the disease, they will express it. On the other hand, girls have two X chromosomes, so if they inherit one copy of the recessive allele, they will be carriers and they won't be affected.
This disorder is never seen in females because they need to have two copies of the recessive allele. However, to have double copy, they should inherit one copy from their mothers and one copy of their fathers, but boys with the allele are affected and they die in early teens without having progeny. Therefore, a girl can't have a "carrier-father", so they will never have two copies to express the disorder.
An endothermic reactions involves absorption in which energy is on the reactant side of the question or the left side. Exothermic involves the release of energy in which energy is on the product side of the equation.
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