Introduction:
Genetic screening is a medical test used to detect various diseases by identifying changes in chromosomes, proteins, or genes. It is performed on saliva or blood, while in pregnant women, it is done on amniotic fluid. Early detection of disease can reduce the risk of any cancer possibilities. Genetic screening provides information about any abnormalities during pregnancy.
What Is Genetic Screening?
The medical process of testing a person for the existence of any genetic disease is called genetic screening. This voluntary process which is a part of genetic consultation assesses the changes in the following:
a) Chromosomes - Analysis of genetic changes in the whole chromosome or a part of DNA (deoxyribonucleic acid) or the presence of an extra copy of chromosomes.
b) Genes - Analysis of variation in DNA sequences that might increase the risk of developing a genetic disorder. The scope of gene tests varies from detecting changes in a single nucleotide to the entire genome.
c) Proteins - Any abnormality in the amount or activity level of biochemical proteins or enzymes suggests changes to the DNA.
When Is Genetic Screening Recommended?
Although some genetic disorders are not hereditary and thus cannot be identified by screening of parents, genetic screening is particularly recommended when:
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One or both partners have a genetic abnormality.
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Family members with a genetic abnormality.
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Partners who belong to a high-risk group.
How Is Genetic Testing Done?
The test is usually requested by a person’s doctor or genetic counselor. Before the tests, the individual is informed thoroughly about the benefits, limitations, and possible consequences of the test, known as informed consent. The tests are done on samples from hair, skin, amniotic fluid, blood, and other tissues like the inner surface of the cheek (buccal smear). The sample is then sent to a laboratory where depending on the suspected disorder, the technician looks for specific changes in chromosomes, DNA, or proteins. Screening tests for newborns are usually done using a small blood sample from the baby’s feet. The direct-to-consumer testing option is also available for people who do not need to go to a healthcare provider to obtain a test and, therefore, can directly contact the testing company.
What Are the Various Types of Genetic Tests?
Depending on what condition is suspected in a person, the healthcare provider or genetic counselor selects the appropriate test. If a diagnosis is non-conclusive, a test that looks at multiple genes or chromosomes may be used. However, if a specific condition is suspected, a more focused test is usually preferred.
1. Molecular Tests: Assess changes in one or more genes. They determine the order of nucleotides in one's genetic code, known as DNA sequencing. Types of molecular tests are:
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Targeted Single Variant - Identifies a specific variant in one gene known to cause the disorder. Example testing for HBB (hemoglobin subunit beta) gene for sickle cell anemia.
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Single Gene Test - Identify mutational changes in one gene. They are helpful in ruling out a diagnosis when there are multiple variants in the suspected gene.
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Gene Panel - Identify variants in more than one gene. Often useful to delineate a diagnosis when the symptoms fit a wide array of conditions. For example, epilepsy has multiple genetic causes.
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Whole Exome Sequencing - They analyze a significant amount of a person’s DNA to find the genetic variation. Usually done when single gene tests provide inconclusive results.
2. Chromosomal Tests: They analyze whole chromosomes or DNA to identify large-scale changes, like an extra or a missing copy of a chromosome. For example, William’s syndrome is caused by the deletion of a section of chromosome 7.
3. Gene Expression Tests: Identifies which genes are expressed or active in different types of cells. They study the mRNA (messenger RNA (ribonucleic acid)) in cells. Overexpression or underexpression of a certain gene may be responsible for various types of cancer.
4. Biochemical Tests: These tests study the quantity as well as the quality of proteins as well as enzymes that are transcribed and translated by the genes.
What Are the Diseases Which Can Be Detected by Genetic Screening?
The diseases which are detected by genetic screening are as follows:
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Obesity: It is one of the most common conditions or diseases in people with a basal metabolic index (BMI) higher or equal to 30 who are characterized as obese.
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Bipolar Disease: It is a disorder associated with multiple mood variations and severe mental illness. It is one of the common hereditary diseases.
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Breast and Ovarian Cancer: It is associated with uncontrolled growth of cells in the breast. Women are 15 to 40 times at risk of developing ovarian cancer due to hereditary issues.
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Vision Loss: Age-related vision disorder after the age of 60 years. The brain stops transmitting clear images to the brain in loss of vision. About 30% of people are diagnosed with vision loss as a result of hereditary reasons.
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Psoriasis: It is symptomized with scaly and red lesions that appear on any part of the body and causes skin inflammation and irritation.
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Dyslexia: Dyslexia is difficulty in reading faced by an individual and is a neurological condition. Its prevalence has been seen since early childhood.
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Parkinson's Disease: It is a neurological disease caused by reduced brain cells that produces dopamine. The symptoms include shaking the face, hands, legs, and jaw, inability to form a firm grip, and dropping things.
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Down’s Syndrome: It is a disorder that causes distinctive physical features, intellectual disabilities, and various other problems. It is a chromosomal disorder that can be detected by genetic screening.
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Huntington's Disease: It is a disorder that affects the brain and usually occurs between the age group of 30 and 50 years.
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Cystic Fibrosis: It is an inherited disease that causes thick and sticky mucosa that builds up in the organs, including the pancreas and lungs.
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Sickle Cell Anemia: It is a disorder that affects red blood cells and is often found in Americans, Hispanics, and Africans. Genetic screening is the best option to detect sickle cell anemia.
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Phenylketonuria: It is a disorder in which levels of phenylalanine level build up in the blood. If left untreated can cause brain damage and heart attack.
Conclusion:
Genetic screening benefits high-risk individuals with prevention and early treatment. Advancements in the field of genetics have made it possible to detect numerous genetic conditions. A balanced and informed approach to the development of genetic policies and regularizations must be followed to promote greater equality and support vulnerable groups susceptible to various hereditary diseases.
