What are genes?

What exactly are genes made of?

Genes are segments of deoxyribonucleic acid (DNA), the complex molecule that carries genetic information in all living organisms. DNA is structured as a double helix, resembling a twisted ladder, where the "rungs" consist of four chemical bases: adenine (A), cytosine (C), guanine (G), and thymine (T). The specific sequence of these letters forms a code that the body reads to assemble proteins.

While humans possess roughly 20,000 to 25,000 genes, these represent only about 1 to 2 percent of the total human genome. The remaining DNA serves various regulatory roles, such as turning genes on or off at specific times during development. Genes are organized into long, tightly coiled structures called chromosomes, which reside within the nucleus of nearly every cell in your body.

How do genes determine my traits?

Genes function by providing the blueprint for proteins, which are the workhorses of the body. Through a process called gene expression, the cell transcribes DNA into messenger RNA, which is then translated into a specific protein. These proteins perform essential tasks, such as building muscle tissue, facilitating chemical reactions, or transporting oxygen through the bloodstream.

Inherited traits are the result of the specific versions of genes, known as alleles, that you receive from your parents. Because you inherit two copies of every gene—one from your mother and one from your father—the interaction between these alleles determines your observable characteristics. This inheritance follows specific patterns:

• Dominant traits appear even if you only inherit one copy of the gene.
• Recessive traits only appear if you inherit two copies of the gene, one from each parent.
• Polygenic traits, such as skin color or height, are influenced by the interaction of many different genes working in concert.

How to understand your genetic risks

Genetic testing allows individuals to identify variations in their DNA that might increase the risk of developing certain medical conditions. These tests analyze specific genes to look for mutations, which are permanent alterations in the DNA sequence. While having a mutation does not guarantee you will develop a disease, it provides valuable data for preventative healthcare.

If you are considering genetic testing, follow these structured steps to ensure you receive accurate and actionable information:

1. Consult with a board-certified genetic counselor to discuss your family health history and the purpose of the test.
2. Select a reputable clinical laboratory that is certified by organizations like the Clinical Laboratory Improvement Amendments (CLIA).
3. Review the results with a medical professional who can translate the findings into a personalized health management plan.
4. Keep your records updated as new research emerges, as the interpretation of genetic data can change over time.

Why do genetic mutations happen?

Mutations are natural occurrences that happen when DNA is copied during cell division. While the body has sophisticated repair mechanisms to fix errors, some changes persist. These mutations can be caused by environmental factors, such as exposure to ultraviolet radiation, chemical carcinogens, or simply by random chance during the replication process.

Most mutations are harmless and contribute to the genetic diversity that defines a species. However, some mutations can disrupt the production of vital proteins, leading to genetic disorders. It is important to distinguish between germline mutations, which are inherited from parents and present in every cell, and somatic mutations, which occur after conception and are restricted to specific tissues or organs.

Common mistakes when interpreting genes

A frequent error is the misconception of "genetic determinism," the belief that your genes dictate your entire destiny. In reality, the environment plays a massive role in how genes are expressed, a field of study known as epigenetics. Factors like diet, stress, exercise, and exposure to toxins can chemically modify how your genes function without changing the underlying DNA sequence itself.

Another common mistake is over-relying on direct-to-consumer ancestry tests for medical advice. These kits are often designed for genealogical exploration rather than clinical diagnosis and may lack the sensitivity required to detect rare, medically significant mutations. Always avoid making major lifestyle changes based solely on home testing kits without validating the findings through a clinical setting. By understanding that genes are merely one part of a complex biological system, you can better appreciate the interplay between your inherited code and the lifestyle choices you make every single day.