subject: Causal Factors of Cri Du Chat Syndrome [print this page] Unbalanced Translocation Unbalanced Translocation
When a part of a chromosome breaks and attaches to a different chromosome, the process is referred to as translocation. If there is no loss or gain of material during this process, it is called balanced translocation which does not affect the individual. However, when there is a loss or gain, it refers to unbalanced translocation and results in a genetic disorder. In case of the occurrence of a balanced translocation in a parent, there are 10% chances for unbalanced translocation to occur in the new-born child. But there are also cases, wherein the child experiences a de novo or spontaneous unbalanced translocation at times.
Ring chromosome
In some rare cases, there are chances where the chromosome just loses a part or piece from each of its ends and these ends can unite to form a ring. In the child who possesses cri du chat syndrome, this ring can lead to further problems based on the amount and length of genetic material lost. And especially, when the loss is from the chromosome's long arm, it is very likely to result in the occurrence of the syndrome.
Interstitial Deletion
In some other cases, a portion from inside of the short arm of the chromosome can get deleted or cut and the broken ends can rejoin. The cut off portion can just be lost or it can get attached to a different chromosome.
Inversion
A chromosome can break at more than a single point sometimes. When it does at two points in the arm, this broken portion can flip, invert and reattach to the chromosome. Owing to the reversal in genetic code in this particular section, there are chances for the occurrence of the syndrome.
Duplication/ Partial Trisomy
A portion of the short arm in the chromosome number five can get duplicated at times and when this includes the critical region of the chromosome, it can result in a disorder. The duplicated portion will attach within the chromosome or at its ends and the code will be misread.
Mosaicism
In rare cases, the deleted chromosome can be present in some cells of our body rather than in all. This content may vary like 20% or 75%. Based on the occurrence of the deletion in the types of body cells and the percentage of occurrence, the child can either be mildly or severely affected. This case presents a difficult diagnosis, since the portion of blood or tissue sample collected must contain the cells with deletion or it would result in a wrong diagnosis.
