Structural Chromosome Anomalies

Translocations

They are structural chromosomal disorders that occur as a result of part exchange between chromosomes. It has two types, reciprocal and Robertsoniant translocation. Most of the time, while the individual with the translocation is chromosomally stable, imbalance may occur in the gamete cells (sperm or egg) during meiosis cell division. Depending on this situation, early or late pregnancy losses, stillbirths or baby births with severe disease findings may occur. While the incidence of translocations in newborn individuals is 1/1000; Rate in couples with 3 or more pregnancy losses

It increases to 3-5%.

Reciprocal Translocation

It is the reciprocal exchange of fragments from two different non-homologous chromosomes between chromosomes.

Robertsonian Translocation

It occurs when one chromosome completely attaches to another chromosome. It forms the most common type of translocation.

Inversion

It occurs when a fracture occurs at two different points of a chromosome and the segment between the fractures rotates 180 degrees. They are called pericentric and paracentricinversions, depending on whether they contain the centromere region or not. Unlike other structural chromosomal disorders such as deletion or duplication, inversions have less change in genetic material, so they are less likely to cause problems in the individual. However, it may have different effects depending on the site of the fracture and the genes affected. During meiosis cell division there is also the possibility of forming unstable gametes. Pericentricinvesion of the 9th chromosome is observed in approximately 1-3% of the population. The incidence is increasing in infertile individuals.

Deletions

Deletion is defined as the loss of any part of the chromosome. Deletions with a size of 1-5 megabases are called microdeletions and can be detected by FISH technique. For smaller deletions, advanced genetic analysis is required. 22. Di-George Syndrome, which occurs as a result of the loss of q11.2 region of the chromosome and causes severe cardiac anomalies, is the most common type of deletion in the fetus and newborn babies

Deletion of the AZF region, which is responsible for sperm production on the Y chromosome, is observed at a rate of approximately 10-15% in men with no sperm in their semen, and 5-7% in men with low sperm count. Depending on the size of the deletion, it may not always be detected in chromosome analysis. For this, the Y chromosome must be confirmed by microdeletion analysis.

If the test result is not normal, a genetic consultation should be obtained by a geneticist about the disorder detected and the problems it may cause.