G scanning / G-chip

1. Technical aspect

 

G-scanning is a postnatal genetic screening to detect chromosomal abnormalities in new born baby using microarray and FISH. The typical 30 chromosomal abnormalities occur in about 1 of 200 newborns, which is highly frequent compared with congenital metabolic disorders which occur in 1 of thousands of newborns. This shows the importance of postnatal genetic screening. In general, physical deformities or disabilities are regarded as inheritance disorders. If a baby’s appearance is fine, people do not realize the need of the screening. However, it is difficult to identify chromosomal disorders by the phenotype, some chromosomal disorders like Turner syndrome and Klinefelter syndrome do not express symptoms in newborns. Chromosomal disorders with developmental delays or mental retardation may not be recognized until a certain developmental stage. Some patients who have chromosomal aberrations, such as Klinefelter syndrome (47, XXY) or Turner synderomd (45, X), do not exhibit clinical features until after a certain year of age. Although there are no cures for chromosomal disorders, many patients without distinct clinical features can be effectively mnanaged and treated in the early stages of development by early diagnosis with array CGH. In addition to the high frequency of diseases associated with chromosomal aneuploidies, detecting chromosomal abnormalities at an early age is very important for the optimal management and treatment of the affected newborns. Hence, early diagnosis is critical in order to begin management and provide the best treatment options for the better life.

2. Procedure

 

G-chip is a DNA chip designed for high-resolution screening. DNA fragments which represent the major region of human chromosome are attached to the chip. In a clinic, blood samples are collected and sent to a laboratory. In a laboratory, DNA is extracted from white blood cell, labeled with green fluorescent dye, and hybridized. To determine numerical and structural chromosomal abnormalities, normal DNA labelled with red fluorescent dye is competitively hybridized as a control.