What is Genetic Testing? A Guide to the Right Test for Your Purpose

Rewritten on: March 30, 2025

Genetic testing analyzes DNA base sequences to check for disease diagnosis and constitutional tendencies. This article explains in detail the differences between hospital genetic testing and DTC genetic testing, the differences from chromosome testing, and the right test to choose for each purpose.

In recent years, genetic testing has advanced dramatically along with rapid technological progress, and it is now widely used in fields ranging from medicine and healthcare to forensic science. However, even though the term "genetic testing" is now heard more often, few people fully understand what such tests actually involve or which test is best suited to their own needs. This article provides a comprehensive explanation—from the basic mechanisms of genetic testing, to the differences between hospital genetic testing and DTC genetic testing, the differences from chromosome testing, and the right test to choose for each purpose.[ref:1]

What Is Genetic Testing?

Genetic testing analyzes the order (base sequence) of the four bases that make up the DNA (deoxyribonucleic acid) forming our bodies—namely A (adenine), G (guanine), C (cytosine), and T (thymine). The entire human genome contains about 3 billion base pairs, and by reading specific regions within this enormous amount of information, it becomes possible to obtain various kinds of health information.[ref:2]

Because the genes related to health are essentially the same in all people, genetic testing compares the subject's sequence against a standard base sequence based on international databases to determine what differences (variants) exist. For example, if the normal sequence "CTGAGGT" appears as "CTGTGGT" in a sample, this indicates a "variant" in which the middle A has been replaced by a T. By analyzing the presence and type of such variants, it is possible to obtain a wide range of information, including disease diagnosis, disease risk prediction, and constitutional tendencies.

Genetic testing technology has advanced dramatically with the advent of next-generation sequencers (NGS). Compared to the traditional Sanger method, it is now possible to read large volumes of DNA sequence in a short amount of time, and as testing costs have fallen, genetic testing has become increasingly accessible to the general public.[ref:3]

Genetic Testing at Hospitals

While the term "genetic testing" is used broadly, tests conducted at hospitals under a doctor's direction differ significantly from those that individuals can order directly online, in terms of purpose, accuracy, and how the results are used.

Genetic testing at hospitals is generally performed to confirm a diagnosis or to select the optimal treatment. A representative example is genetic testing in cancer treatment. "Cancer genome profiling tests," which comprehensively examine genetic mutations in cancer cells, can identify the type of cancer and determine which anticancer drugs are likely to be most effective. This is helping to realize "precision medicine," in which treatment is optimized for each individual patient.[ref:4]

In addition, for "single-gene disorders" such as phenylketonuria or Marfan syndrome—conditions in which a mutation in a single gene directly causes the disease—genetic testing can provide a definitive diagnosis. Testing an individual's sensitivity to medications (pharmacogenetics) is another important use; because people with certain genetic variants metabolize drugs differently, knowing this in advance allows for safer prescribing.[ref:7]

• Identifying genetic mutations in cancer cells to select the optimal treatment drug
• Definitive diagnosis of single-gene disorders (such as phenylketonuria)
• Assessing drug sensitivity to create a safer medication plan
• Carrier testing for hereditary diseases
• Genetic counseling and risk assessment based on family history

DTC Genetic Testing

In contrast to hospital-based genetic testing, DTC (Direct-to-Consumer) genetic testing is a service that individuals can order directly, without going through a medical institution, via online retailers or drugstores. A test kit is delivered to your home, and results are obtained simply by returning a saliva or other sample—a hallmark of its convenience.[ref:1]

DTC genetic testing mainly analyzes SNPs (single nucleotide polymorphisms)—differences in genetic information between individuals. Human DNA sequences are up to 99.9% identical across all people, but the remaining 0.1% of variation accounts for differences in individual constitution, appearance, and disease susceptibility. DTC genetic testing statistically analyzes this SNP information and presents disease risk and constitutional tendencies as probabilities, based on research papers and genome-wide association study (GWAS) results.

• Risk of lifestyle diseases (diabetes, high blood pressure, etc.)
• Predisposition to obesity and suitability for weight loss
• Alcohol metabolism ability and caffeine sensitivity
• Beauty-related items such as skin quality and hair-loss risk
• Muscle characteristics and athletic aptitude

However, it is important to note that most diseases are influenced by a complex interplay of multiple genes as well as significant environmental factors (diet, exercise, stress, etc.), so DTC genetic test results only indicate statistical tendencies. Because a diagnosis of disease cannot be made based on DTC genetic test results alone, you should always consult a medical institution if you have concerns about your results.[ref:5]

Differences from Chromosome Testing

While genetic testing examines minute variants at the level of DNA base sequences, chromosome testing operates on a much larger scale, examining the number and shape (structure) of "chromosomes," the structures into which DNA is folded.

Human chromosomes normally consist of 46 in total: 22 pairs (44) of autosomes and 1 pair (2) of sex chromosomes (XX in females, XY in males). Chromosomal abnormalities are broadly divided into two types: "numerical abnormalities" and "structural abnormalities." A well-known example of a numerical abnormality is "trisomy 21 (Down syndrome)," in which there are three copies of chromosome 21. Structural abnormalities include "translocation," in which part of a chromosome attaches to another chromosome; "deletion," in which part of a chromosome is lost; and "inversion," in which part of a chromosome is reversed.

The main purposes of chromosome testing include diagnosing cancer and leukemia, diagnosing congenital disorders, and NIPT (Non-Invasive Prenatal Testing), which examines fetal chromosomal abnormalities before birth.[ref:6] As this shows, genetic testing and chromosome testing clearly differ in what they examine and their purposes, so it is important to choose the appropriate test depending on the situation.

Choosing the Right Test for Your Purpose

So far we have explained the types of genetic testing and how they differ from chromosome testing, but the optimal test method depends on your own purpose. Below, we introduce the right test to choose for each purpose in an easy-to-understand way.

1. Confirming a parent-child relationship → Paternity DNA testing
2. Confirming parentage before birth → Prenatal paternity DNA testing
3. Determining a fetus's sex → Next-generation fetal sex testing
4. Confirming a sibling relationship → Sibling/relative DNA testing
5. Confirming an animal's blood relationship → Animal paternity DNA testing

① Genetic Testing to Confirm Whether Someone Is Your True Parent

For those who wonder "Is this really my parent?" or "Is this child really mine?," paternity DNA testing using next-generation DNA testing methods is the ideal choice. Every person inherits half of their DNA information from their father and half from their mother, and this genetic information never changes throughout life. Paternity DNA testing analyzes multiple specific regions of DNA known as STRs (short tandem repeats) and statistically evaluates whether the DNA types are inherited consistently between parent and child.[ref:8]

About Paternity DNA Testing (Father-Child / Mother-Child)

② Genetic Testing to Confirm Parentage Before Birth

For those who feel anxious during pregnancy about "whether this is really my child," "prenatal paternity DNA testing" is the appropriate option. This test determines parentage before birth by comparing fetal-derived cell-free DNA (cfDNA) contained in the mother's blood during pregnancy with a sample from the alleged father. Because it only requires a blood sample from the mother, it is a non-invasive method, offering greater safety than tests such as amniocentesis, which carry a risk of miscarriage.

About Prenatal Paternity DNA Testing

③ Genetic Testing to Learn Your Baby's Sex Early

For those who want to know their baby's sex as early as possible during pregnancy, "next-generation fetal sex testing" is recommended. While ultrasound at an obstetrics clinic can typically confirm sex around week 16 of pregnancy, this test can be performed from as early as week 7. It analyzes fetal-derived DNA contained in the mother's blood and determines sex with high accuracy by checking for the presence of the Y chromosome.

Next-Generation Fetal Sex Testing

④ Genetic Testing to Confirm Whether Siblings Are Truly Related

For those who wonder "Are we really blood-related siblings?," we recommend sibling/relative DNA testing using next-generation DNA testing methods. DNA testing between siblings can require somewhat more complex statistical analysis compared to paternity testing, but thanks to its extensive experience and advanced analytical techniques, seeDNA is also able to determine whether siblings are full siblings (sharing both parents) or half-siblings (sharing only one parent).

Sibling/Relative DNA Testing

⑤ Genetic Testing to Learn the Blood Relationship of Pets or Animals

If you want to confirm the blood relationship of a pet or animal you keep, or need proof of parentage for pedigree registration, animal paternity DNA testing is available. Many mammals, including dogs, cats, and horses, can undergo paternity testing using DNA profiles, just like humans. This is also an important test for breeders and those in the livestock industry, and it can be used with confidence.

Animal Paternity DNA Testing

Points to Know Before Undergoing Genetic Testing

There are several important points to keep in mind when undergoing genetic testing. First, it is important to correctly understand the purpose and limitations of the test. The disease risks shown by DTC genetic testing are only statistical probabilities and do not mean the disease will definitely occur. On the other hand, genetic testing performed at medical institutions can sometimes lead to a definitive diagnosis, so the weight of the results differs.[ref:5]

In addition, because the information obtained from genetic testing is genetic information that never changes over a lifetime, protecting privacy is extremely important. When choosing a reliable testing institution, we recommend checking its personal information management practices and data handling policies. In Japan, the "Guidelines on Genetic Testing and Diagnosis in Medical Care" have been established, setting out standards for the proper implementation of genetic testing and the protection of personal information.[ref:9] If you have any concerns or questions about your test results, it is advisable to consult a genetic counselor or specialist physician.[ref:4]

Summary

This article explained in detail the mechanisms and types of genetic testing, as well as the right test to choose for each purpose. Genetic testing spans a wide range—from medical testing performed at hospitals to DTC genetic testing and chromosome testing—each examining different things and yielding different types of information. To choose the test method best suited to your own purpose, it is important to correctly understand the characteristics and limitations of each test.

If you are considering DNA testing or genetic testing, we hope this article serves as a useful reference, and we encourage you to consult a specialized testing institution as needed. The seeDNA Genetic Medicine Research Institute provides a wide range of DNA testing services—including paternity DNA testing, prenatal paternity DNA testing, fetal sex testing, and sibling/relative DNA testing—with high accuracy and reliability.

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Frequently Asked Questions

Q1. What is the difference between genetic testing and DNA testing?

A. Genetic testing analyzes DNA base sequences to check for disease diagnosis and constitutional tendencies. DNA testing, on the other hand, is primarily aimed at creating a DNA profile to identify individuals and determine parent-child or blood relationships. Both involve analyzing DNA, but they differ in purpose and analytical method.

Q2. How reliable are DTC genetic test results?

A. DTC genetic test results present disease risk and constitutional tendencies as "probabilities" based on statistical SNP (single nucleotide polymorphism) data; they are not a definitive medical diagnosis. Because most diseases are influenced by a combination of multiple genes and environmental factors, it is recommended that you treat the results as reference information only and consult a medical institution if anything concerns you.[ref:1]

Q3. How should I choose between genetic testing and chromosome testing?

A. Genetic testing examines minute variants at the level of DNA base sequences and is used for diagnosing single-gene disorders and for cancer genome profiling. Chromosome testing examines the number and structure of chromosomes (such as translocations or deletions) and is used for diagnosing trisomies such as Down syndrome, as well as for NIPT. The appropriate test depends on what you want to investigate, so please consult a specialized institution.

Q4. Does prenatal paternity DNA testing pose any risk to the fetus?

A. seeDNA's prenatal paternity DNA testing is a non-invasive method that analyzes fetal-derived cell-free DNA (cfDNA) contained in the mother's blood. Because it does not require inserting a needle into the uterus, as with amniocentesis or chorionic villus sampling, there is no risk of miscarriage and no impact on the fetus. The test can be performed using only a blood sample drawn from the mother's arm.

Q5. Can genetic test results change in the future?

A. While an individual's genes (DNA sequence) themselves never change over a lifetime, the "interpretation" of DTC genetic test results can change. This is because research into the relationship between genes and disease advances daily, and as new findings emerge, the statistical data is updated. As a result, even with the same SNP data, risk assessments may be revised in the future.[ref:5]

Q6. Is my privacy protected when undergoing genetic testing?

A. Reliable testing institutions maintain strict systems for protecting personal information. The seeDNA Genetic Medicine Research Institute has obtained the international quality standard ISO 9001 and the Privacy Mark for personal information protection, and properly manages all personal data, including genetic information. When choosing a testing institution, we recommend checking its privacy policy and data management practices in advance.

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