Understanding Your DNA, Genes, and How They Can Affect Medication Response

You don’t need to be a geneticist to understand your genes.

Every cell in your body contains genetic information that helps your body grow, function, repair itself, and respond to its environment. Your genes also provide instructions for making many of the proteins your body needs—including proteins that help process medications and proteins that medications interact with.

Let’s break it down.

What is a cell?

Your body is made up of trillions of cells.

Cells are the basic building blocks of your body. Different cells have different jobs. For example, brain cells communicate with each other, liver cells help process substances, and muscle cells help you move.

Almost every cell contains a nucleus, which stores your genetic information.

Think of a cell as a small factory—and your DNA as the instruction manual inside it.

What is DNA?

DNA (deoxyribonucleic acid) is the molecule that stores your genetic instructions.

DNA contains a chemical code made from four building blocks:

A, T, C, and G

The order of these letters contains biological instructions.

You can think of DNA as a very large instruction manual written in a four-letter code.

What are chromosomes?

DNA is extremely long, so your cells organize it into structures called chromosomes.

Most people have 23 pairs of chromosomes—46 chromosomes in total.

You receive one chromosome in each pair from your biological mother and one from your biological father.

Chromosomes are like organized volumes of your DNA instruction manual.

What is a gene?

A gene is a specific section of DNA that contains instructions for a particular biological function.

Some genes contain instructions for making proteins. Other genes help control when and where genes are turned on or off, and some provide instructions for functional RNA molecules.

A simple way to think about it is:

DNA → contains genes → genes provide biological instructions → cells use those instructions to make or regulate important molecules

Your genes help determine how your body works, but they are not the only factor. Environment, lifestyle, age, other health factors, and medications can also influence how your body functions.

What are proteins?

Proteins are some of the body’s most important working molecules.

Many genes provide instructions for making proteins, and these proteins perform different jobs throughout the body.

Different genes can make different types of proteins

• EnzymesHelp chemical reactions happen in the body.
• For example, some enzymes help break down medications.
• ReceptorsReceive signals from chemicals such as neurotransmitters or medications.
• Receptors can influence how cells respond to signals.
• TransportersHelp move substances into, out of, or within cells.
• Some transporters influence how medications move through the body.
• Structural proteinsHelp build and maintain cells and tissues.
• Signaling proteinsHelp cells communicate with one another and regulate biological processes.
• Regulatory proteinsHelp control when genes and other cellular processes are turned on or off. So, genes don’t simply determine a person’s traits. They provide instructions that help create and regulate the biological machinery that allows the body to function.

What happens when a gene has a change?

DNA is not exactly the same in every person.

Small differences in DNA are called genetic variants.

Many genetic variants have no meaningful effect at all.

However, some variants can change how a gene works. A change may affect:

• How much of a protein is produced
• How well a protein works
• How quickly a protein works
• How stable the protein is
• Where the protein is found in the body
• Whether the protein works at all Think of a gene as a recipe.

If there is a small change in the recipe, the final product might be:

Exactly the same → Slightly different → More active → Less active → Not produced

The effect depends on the specific genetic change and the biological function of that gene.

A simple example: medication metabolism

Some genes provide instructions for making enzymes that process medications.

For example, enzymes in the liver help break down many medications.

If a genetic variant changes how an enzyme works, a person may process a particular medication:

• More slowly The medication may remain in the body longer, potentially increasing exposure and the risk of side effects.

• More quickly The medication may be cleared from the body faster, potentially reducing medication exposure and effectiveness.

• Normally The genetic variant may have little or no clinically meaningful effect on the medication.

This is one reason why the same dose of the same medication can affect two people differently.

But metabolism is only part of the story

How quickly your body processes a medication is called pharmacokinetics.

But there is another important question:

What happens when the medication reaches its target?

This is related to pharmacodynamics.

Some genes provide instructions for proteins such as receptors, transporters, or other biological targets involved in how medications produce their effects.

A genetic difference in one of these proteins may influence how a person’s body responds to a medication—even when the medication is being processed normally.

This means:

Normal metabolism does not always mean normal medication response.

Medication response can involve both:

Pharmacokinetics

How your body processes the medication

Pharmacodynamics

How the medication interacts with your biology

Why do genetic differences matter?

Imagine two people taking the same medication at the same dose.

Person A may process the medication at an expected rate and respond well.

Person B may process it much faster or slower—or may have biological differences that influence how the medication interacts with its targets.

Both people are taking the same medication.

But their biology is not necessarily the same.

This is one reason medication treatment can sometimes involve trial and error.

What is pharmacogenomics?

Pharmacogenomics (PGx) looks at how a person’s genetic differences may influence their response to medications.

A PGx test examines selected genetic variants that have been studied for their potential relationship with medication metabolism, transport, targets, or response.

The goal is not to predict the future with certainty.

Instead, genetic information can provide additional information about the individual patient that may help inform medication decisions.

Genetics is one piece of the puzzle

Your genes are important—but they are not the whole story.

Medication response can also be influenced by:

• Age
• Other medications
• Medical conditions
• Lifestyle
• Diet
• Kidney and liver function
• Dose
• How consistently the medication is taken
• Other biological and environmental factors That is why genetic information should be considered alongside the patient’s clinical history and other relevant information.

The Picture

Think of your body as a complex system:

CELLS↓

contain

CHROMOSOMES↓

which organize

DNA↓

which contains

GENES↓

that provide instructions for making or regulating

PROTEINS & OTHER BIOLOGICAL MOLECULES↓

which perform different functions throughout the body

A change in DNA can sometimes change how a protein functions.

And when that protein is involved in medication metabolism, transport, or biological response, the genetic difference may help explain why people can respond differently to the same medication.

Your genes don’t tell the whole story. But they can tell an important part of it.

Personalized Prescribing

Using genetic information to help support more informed medication decisions.