Cytogenetic and molecular investigation of terminal deletion of the long arm of chromosome 7 in three cases
Chromosomal anomaly is an abnormality of the number or structure of the chromosome. Based on this, they are classified as either numerical or structural. These anomalies can have a mild or severe effect on the phenotype of the carrier which depends on the chromosomal region involved and the genes implicated. They can be sporadic or inherited. Thus, it is essential to investigate such anomalies both prenatally and postnatally alike. In a standard cytogenetic lab, these anomalies can be detected using low-resolution or high-resolution karyotype, usually by performing GTG (G-bands by trypsin using Giemsa) on chromosomes undergoing mitosis, derived from blood. If higher resolution is required, there are various other molecular cytogenetic techniques available like FISH and microsatellite analysis. More recently, microarrays have opened a new era in the field of molecular genetics by greatly increasing the resolution of screening for copy number gains and losses. Using these techniques, we characterized deletions in the long arm of chromosome 7 in three clinical cases, identified the breakpoint, studied the inheritance pattern and compared our cases with the other cases carrying similar deletion in the literature. It was observed that the deletion was located at 7q36.2, 7q35 and 7q36.1 for cases 1, 2 and 3 respectively. Case 3 also carried a duplication of Xq28.