autosomal recessive

• Incidence of severe recessive disorders that are sex linked are rare because it is unlikely that a carrier from one family will mate with another carrier of the same recessive condition 

  In consanguineous marriage (when couple are close relatives e.g. cousins), chance of both being a carrier for a recessive allele is greater
• PHENYLKETONURIA (PKU)

  Gene concerned controls production of enzyme phenylalanine hydroxylase

  This enzyme converts the amino acid phenylalanine to tyrosine

  If not present, phenylalanine will accumulate in the bloodstream becoming toxic

  The toxicity results in damage to the growing brain
• PKU

  Causes : 

  • Extreme mental retardation
  • Tendency towards epileptic seizures
  • Failure to produce normal skin pigmentation
• PKU

  Normally, phenylalanine is an essential amino acid and must be present in the diet, enough must be present so that a child may grow

  For people with PKU, excessive amounts of phenylalanine in the diet can be dangerous

  Special diets restricting intake of phenylalanine can largely, if

  not entirely, correct the symptoms
• CYSTIC FIBROSIS

  Causes : 

  • Chest infections
  • Lack of digestive enzymes
  • Increased salt loss
• CYSTIC FIBROSIS

  Special diet low in fat, high in carbohydrate and protein

  Diet is supplemented with pancreatic extract and large doses of vitamins A, D and K

  • Does not cure the disease
  • Enable the child to function as normally as possible
• Blood prick from baby’s heel 2-3 days after they are born can diagnose conditions