PKU

PKU

Genotype
1. Alleles: Different forms of a gene.
  1. Normal/wildtype allele
  2. Defective/mutant/disease-causing allele
  3. Individuals with 2 normal alleles are phenotypically normal
    1. Produce lots of phenylalanine hydroxylase
  4. Individuals with 1 normal allele and 1 defective allele are phenotypically normal
    1. Produce adequate amounts of phenylalanine hydroxylase
  5. Individuals with two defective alleles have PKU
    1. Do not produce a functional phenylalanine hydroxylase
Recessive condition because the affected individual must have two copies of the defective allele
Chromosomes
1. Humans have 46 chromosomes
  1. 2 of each - chromosome number (1-22) and XX or XY
2. Chromosomes 1-22 are called autosomes
3. X and Y chromosomes are called sex chromosomes
  1. Y chromosome has gene for males
4. The gene that encodes phenylalanine hydroxylase is found on chromosome 12
PKU is an autosomal recessive disease
How common is PKU?
1. Northern Europe: 1 in 10,000
2. Ireland: 1 in 4,500
3. U.S. Whites - 1 in 8,000
4. U.S. Blacks: 1 in 50,000
5. Incidence of PKU is approximately 1 in 10,000 births in Ontario
Newborn Screening
1. Babies tested shortly after birth for PKU
2. The Guthrie Test
  1. Blood sample taken
    1. Blood is placed on a plate with bacteria that need phenylalanine to grow
      1. A positive test that shows a halo of growing bacteria surrounding spots with excess phenylalanine
3. Mass spectrometry is now used to detect elevated levels of phenylalanine in a newborn's blood
Dietary management of PKU
1. Reduce intake of phenylalanine
2. Diet includes protein supplements in which phenylalanine is reduced
3. Special formula for infants and toddlers
4. Protein mixes for children and adults
5. Avoid aspartame
PKU and Pregnancy
1. Women with PKU must resume the special diet during pregnancy
2. Excess phenylalanine in the blood can cross the placenta and damage the foetus

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	Criado por clairegillian95 mais de 10 anos atrás