It was originally used by South African clinicians to describe the effects of exposure to frequent, high levels of violence usually associated with civil conflict and political repression. The term is also applicable to the effects of exposure to contexts in which gang violence and crime are endemic as well as to the effects of ongoing exposure to life threats in high-risk occupations such as police, fire and emergency services. Traumatic grief
Traumatic grief or complicated mourning are conditions where both trauma and grief coincide. There are conceptual links between trauma and bereavement since loss of a loved one is inherently traumatic. If a traumatic event was life-threatening, but did not result in a death, then it is more likely that the survivor will experience post-traumatic stress symptoms. If a person dies, and the survivor was close to the person who died, then it is more likely that symptoms of grief will also develop. When the death is of a loved one, and was sudden or violent, then both symptoms often coincide. This is likely in children exposed to community violence.For C-PTSD to manifest traumatic grief, the violence would occur under conditions of captivity, loss of control and disempowerment, coinciding with the death of a friend or loved one in life-threatening circumstances. This again is most likely for children and stepchildren who experience prolonged domestic or chronic community violence that ultimately results in the death of friends and loved ones.
As an autosomal recessive disorder, two PKU alleles are required for an individual to experience symptoms of the disease. For a child to inherit PKU, both the mother and father must have and pass on the defective gene. If both parents are carriers for PKU, there is a 25% chance any child they have will be born with the disorder, a 50% chance the child will be a carrier and a 25% chance the child will neither develop nor be a carrier for the disease.PKU is characterized by homozygous or compound heterozygous mutations in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional. : 541  This enzyme is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acid tyrosine (Tyr). When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate (also known as phenylketone), which can be detected in the urine.Carriers of a single PKU allele do not exhibit symptoms of the disease but  appear to be protected to some extent against the fungal toxin ochratoxin A. This accounts for the persistence of the allele in certain populations in that it confers a selective advantage—in other words, being a heterozygote is advantageous.The PAH gene is located on chromosome 12 in the bands 12q22-q24.2. As of 2000, around 400 disease-causing mutations had been found in the PAH gene. This is an example of allelic genetic heterogeneity.