Phenylketonuria And Hereditary Diseases

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Phenylketonuria is a genetic desease. Phenylketonuria is caused by a deficiency in PAH
(phenylalanine hydroxylase). This is caracterized by a homozygous mutations of gene of
Hepatic Enzyme Phenylalanine Hydroxylase (PAH). This enzyme is necessary to metabolize phenylalanine (Phe) to tyrosine (Tyr). PAH gene is located on chromosom 12 in 12q24.1.
This desease can be transmitted from the parents to the child.
This desease is an autosomal recessive desease : the affected gene is on one of the twenty two chomosom and the mutation is recessive. The parents can be carrier of the gene : they have one PKU gene and one normal gene. The parents can be affected : they have two PKU gene.
The parents can be non affected and non carrier of the desease : they have the two normal
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We are now going to see the differents possibilities of crossing genes with the percentages. If two persons that carry the gene but who are not affected (carrier of the desease) have children, there are some differents possiblities for the health of the baby. The child can be affected of the desease (25% of chances), the child can be carrier of the desease but not affected (50% of chances) , and the child can be healthy : not affected and not carrier (25% of chances). This situation is illustrated in the two pictures below.
If the parents are both affected, the child will be affected too.
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