UPSC MAINS 2019: Importance of genetic testing

Importance of genetic testing

 

Topic: Importance of genetic testing

Topic in Syllabus: GS Paper  3: Science & Technology

 

 

Importance of genetic testing

Context:

Genetic testing has become extremely popular in the past decade. People have begun making use of the wide variety of resources at hand to test their susceptibility to disease, ancestry, even their athletic ability. As the science of genetic testing continues to develop and provide us with new information about our DNA, certain ethical questions regarding the proper use of these tests come into question.

 

Genetic testing:

Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person’s chance of developing or passing on a genetic disorder. More than 1,000 genetic tests are currently in use, and more are being developed.

 

Methods can be used for Genetic testing:

  • Molecular genetic tests (or gene tests) study single genes or short lengths of DNA to identify variations or mutations that lead to a genetic disorder.
  • Chromosomal genetic tests analyze whole chromosomes or long lengths of DNA to see if there are large genetic changes, such as an extra copy of a chromosome, that cause a genetic condition.
  • Biochemical genetic tests study the amount or activity level of proteins; abnormalities in either can indicate changes to the DNA that result in a genetic disorder.

 

Types of Genetic tests and significance:  

Genetic testing can provide information about a person’s genes and chromosomes. Available types of testing include:

1) Newborn screening:

  • Newborn screening is used just after birth to identify genetic disorders that can be treated early in life. Millions of babies are tested each year in the United States.
  • All states currently test infants for phenylketonuria (a genetic disorder that causes intellectual disability if left untreated) and congenital hypothyroidism (a disorder of the thyroid gland). Most states also test for other genetic disorders.

2) Diagnostic testing:

  • Diagnostic testing is used to identify or rule out a specific genetic or chromosomal condition. In many cases, genetic testing is used to confirm a diagnosis when a particular condition is suspected based on physical signs and symptoms.
  • Diagnostic testing can be performed before birth or at any time during a person’s life, but is not available for all genes or all genetic conditions. The results of a diagnostic test can influence a person’s choices about health care and the management of the disorder.

3) Carrier testing:

  • Carrier testing is used to identify people who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder.
  • This type of testing is offered to individuals who have a family history of a genetic disorder and to people in certain ethnic groups with an increased risk of specific genetic conditions. If both parents are tested, the test can provide information about a couple’s risk of having a child with a genetic condition.

4) Prenatal testing:

  • Prenatal testing is used to detect changes in a fetus’s genes or chromosomes before birth. This type of testing is offered during pregnancy if there is an increased risk that the baby will have a genetic or chromosomal disorder.
  • In some cases, prenatal testing can lessen a couple’s uncertainty or help them make decisions about a pregnancy. It cannot identify all possible inherited disorders and birth defects, however.

5) Preimplantation testing:

  • Preimplantation testing, also called preimplantation genetic diagnosis (PGD), is a specialized technique that can reduce the risk of having a child with a particular genetic or chromosomal disorder.
  • It is used to detect genetic changes in embryos that were created using assisted reproductive techniques such as in-vitro fertilization.
  • To perform preimplantation testing, a small number of cells are taken from these embryos and tested for certain genetic changes. Only embryos without these changes are implanted in the uterus to initiate a pregnancy.

6) Predictive and presymptomatic testing:

  • Predictive and presymptomatic types of testing are used to detect gene mutations associated with disorders that appear after birth, often later in life.
  • These tests can be helpful to people who have a family member with a genetic disorder.
  • Predictive testing can identify mutations that increase a person’s risk of developing disorders with a genetic basis, such as certain types of cancer.

7) Forensic testing:

  • Forensic testing uses DNA sequences to identify an individual for legal purposes.
  • Unlike the tests described above, forensic testing is not used to detect gene mutations associated with disease.
  • This type of testing can identify crime or catastrophe victims, rule out or implicate a crime suspect, or establish biological relationships between people (for example, paternity).

 

Why Genetic testing?

Here are cited reasons why parents have their children (usually at the embryonic or fetal stage) genetically tested:

  • To learn about the presence of a disease that would cause the parent to terminate pregnancy (ex. If they don’t want to raise a child with Down syndrome)
  • To prepare financially and emotionally for a child with certain defects.
  • To discover and treat a disease in the fetus (through surgery, with drugs)
  • To learn information about the baby (though unnecessary to know during pregnancy) such as eye color, sex, their carrier status, their susceptibility to certain diseases that may not threaten them until adulthood, etc.
  • To contribute to scientific understanding of genes and genetic mutations

Here are cited reasons why adults undergo genetic tests:

  • To find out if they are a carrier to a disease that could result in their children’s genome and harm their offspring (and then make reproductive decisions based on this information)
  • To find out if they are susceptible or likely to contract certain diseases in the future
  • If they do have the gene to diseases that may harm them in years to come, to learn about preventative steps that can be taken or to prepare psychologically, financially, etc.
  • To guide doctors on the best way to proceed/provide medical treatment for a disease based on a patient’s genome
  • To find out if they are genetically related to a child (paternity test) which would possibly lead to the father needing to/ceasing to pay money to mother, spending more/less time with child, etc.
  • To learn about where they come from, discover new relatives, learn more about their family history.

 

Direct-to-consumer genetic testing:

Direct-to-consumer (DTC) genetic testing is a type of genetic test that is accessible directly to the consumer without having to go through a health care professional. Usually, to obtain a genetic test, health care professionals (such as doctors) acquire their patient’s permission and then order the desired test. DTC genetic tests, however, allow consumers to bypass this process and order DNA tests themselves.

  • There is a variety of DTC tests, ranging from tests for breast cancer alleles to mutations linked to cystic fibrosis. Benefits of DTC testing are the accessibility of tests to consumers, promotion of proactive healthcare, and the privacy of genetic information.
  • Possible additional risks of DTC testing are the lack of governmental regulation, the potential misinterpretation of genetic information, issues related to testing minors, privacy of data, and downstream expenses for the public health care system.

 

The importance of Genetic testing:

Genetic testing has potential benefits whether the results are positive or negative for a gene mutation. Test results can provide a sense of relief from uncertainty and help people make informed decisions about managing their health care.

  • Genetic testing has potential benefits whether the results are positive or negative for a gene mutation. Test results can provide a sense of relief from uncertainty and help people make informed decisions about managing their health care.
  • A negative result can eliminate the need for unnecessary checkups and screening tests in some cases.
  • A positive result can direct a person toward available prevention, monitoring, and treatment options.
  • Genetic test results can also help people make decisions about having children. Newborn screening can identify genetic disorders early in life so treatment can be started as early as possible.”
  • Genetic testing can provide important information for diagnosing, treating and preventing illness, there are limitations. For example, if you’re a healthy person, a positive result from genetic testing doesn’t always mean you will develop a disease.
  • The result of a genetic test uniquely identifies an individual. As a result, there are many criminal cases that can be solved by placing the subject at the crime scene. First, forensic investigators get samples of blood, hair or tissue from the crime science. Secondly, laboratory technicians can easily verify the identity of the person who is involved in the crime.

 

Risks and limitations associated with Genetic Testing:

  • The physical risks associated with most genetic tests are very small, particularly for those tests that require only a blood sample or buccal smear (a procedure that samples cells from the inside surface of the cheek).
  • The procedures used for prenatal testing carry a small but non-negligible risk of losing the pregnancy (miscarriage) because they require a sample of amniotic fluid or tissue from around the fetus.
  • Many of the risks associated with genetic testing involve the emotional, social, or financial consequences of the test results. People may feel angry, depressed, anxious, or guilty about their results.
  • The potential negative impact of genetic testing has led to an increasing recognition of a “right not to know”. In some cases, genetic testing creates tension within a family because the results can reveal information about other family members in addition to the person who is tested.
  • Some individuals avoid genetic testing out of fear it will affect their ability to purchase insurance or find a job
  • Genetic testing can provide only limited information about an inherited condition. The test often can’t determine if a person will show symptoms of a disorder, how severe the symptoms will be, or whether the disorder will progress over time.
  • Another major limitation is the lack of treatment strategies for many genetic disorders once they are diagnosed.
  • Another limitation to genetic testing for a hereditary linked cancer, is the variants of unknown clinical significance. Because the human genome has over 22,000 genes, there are 3.5 million variants in the average person’s genome. These variants of unknown clinical significance means there is a change in the DNA sequence, however the increase for cancer is unclear because it is unknown if the change affects the gene’s function.
  • For some conditions, even though a changed gene or chromosome is found, it is not possible to tell how severely a person will be affected.

 

Conclusion:

Genetic testing is voluntary. Because testing has benefits as well as limitations and risks, the decision about whether to be tested is a personal and complex one. A geneticist or genetic counselor can help by providing information about the pros and cons of the test and discussing the social and emotional aspects of testing.

 

Sample Question:

What is genetic testing? Discuss the types of genetic tests? Comment on risks associated with genetic tests?