Genetic Counselling and Methods of Genetic Screening
The process of finding the possibility of any inherited disorders through various genetic techniques and tests is called genetic counseling. Through genetic counseling, one can obtain information about genetic problems that may affect him or his family in any way. A genetic counselor determines the possibility of genetic disorders on the basis of the personal and family health history of a person. Through the information on family health history, a genetic counselor advises any genetic test to confirm the possibility of a specific disorder. A couple may go for counseling if they are deciding for pregnancy, during pregnancy, or for caring for a child.
Genetic testing has been improved over the last some decades and many methodologies have bubbled up. But there are three main types of testing are; cytogenic testing (for detecting abnormalities in the chromosomes), biochemical testing (for evaluating the protein functioning), and molecular testing (for detecting mutations in the DNA sequences).
In cytogenic testing, chromosomes are examined to spot the structural abnormalities. Structural abnormalities include deletions, insertions, and translocations. Fluorescence in situ hybridization (FISH) technique is used to stain chromosomes or parts of chromosomes with fluorescent molecules that help in the detection of structural abnormalities. Cells are cultured to fix chromosomes and spread on the slides. Then fluorescent dye is applied to visualize abnormalities.
Biochemical testing is about the detection of protein markers in case of a diseased condition. Inborn errors of metabolism are the basis of many diseases that are present at birth. During biochemical analysis, enzyme activity is assessed by either directly (by measuring the activity of the proteins) or indirectly (by measuring levels of metabolites). Other methods check for the quantity and size of a protein. Tandem Mass Spectroscopy, Gas Chromatography/Mass Spectrometry and High-Performance Liquid Chromatography like techniques are used in biochemical testing.
Molecular testing or DNA analysis is used when a sequence of the gene of interest is known or when a protein biomarker is unknown. A very little amount of sample is required for analysis and any tissue can be used. Hybridization, PCR, and direct sequencing are some common techniques for DNA analysis. Other advanced techniques include Chromosomes microarray analysis, Comparative Genomic Hybridization, and Protein microarray analysis. Many mutations can be the cause of a genetic disorder, in this case, DNA analysis becomes challenging. Therefore, a set of common mutations is studied first before moving towards a comprehensive study.
All methods have their pros and cons and each should be considered by a counselor before recommending a test.