How Traits Are Made

Meet Cecile, Our Video Host

My name is Cecile and I’m a PhD student at the University of Utah. My research is a lot like doing DNA detective work! I look for rare changes in genes that could explain why some kids get autoimmune arthritis, which is when the immune system mistakenly attacks the joints and causes swelling and pain. One day, we hope to discover a new treatment that helps kids and adults with autoimmune arthritis feel better sooner and for longer. When I’m not in the lab, I like to paint, go hiking, and hang out with my friends.

Cecile working in a research lab at the University of Utah

What is a Trait?

Traits like height are easy to see. Others, like musical ability are more hidden.

You can think of a trait as any characteristic of a living thing. It can be physical (like nose shape), a behavior (like language), or internal (like the ability to digest milk). The examples are endless! In fact, a harder question might be: what isn’t a trait? A non-trait is something you can separate from a living thing. Diet, culture, and environment are a few examples of non-traits.

Another important aspect of traits is that they vary. You can compare differences between members of a group—like height across a classroom of students. You can also compare trait differences between groups. For example, some species of reptiles have four legs while other species have none.

Most traits are influenced by multiple genes plus a context—a set of environmental factors. It can be tricky to tell what exactly makes a trait just from looking, but there are clues. Learn more in What Causes a Trait.

Context Means "Environmental Factors"

When you hear the word “environment,” you might think about the weather or air pollution. But in biology, your environment is so much more than that! It includes everything besides DNA that affects your traits.

Nutrients, infections, and hormones are just a few internal environment factors that can shape your traits. And the environment outside your body does include weather and air pollution—but also your relationships, culture, and daily activities. Your environment is the entire context in which you experience life. It’s as unique as you are.

There are many factors beyond genes that shape your traits—no matter what word you choose to describe them.

Trait Differences Come From Genes and Context Too!

To make your traits, it took all your genes plus context (environmental factors). Your unique blend of genes and context is also why your combination of traits is different from anyone else’s.

Gene Differences

Genes are instructions for building proteins. Teams of proteins work together to build the body and make it work. But aside from identical twins, no two people have the exact same genetic information. There are small differences in genes from one person to the next. Differences in genes can lead to differences in the proteins they code for. When proteins work even a little differently, that can affect traits. For example, differences in a bone-building protein can make one person’s elbows or cheekbones look a little different from someone else’s. Across all humans, there are millions of little differences like this.

Context Differences

Environmental factors affect your traits by changing how your genes and proteins are deployed, or how active they are. They can affect where, when, and how much protein is made from a gene. For example, working out activates certain muscle-building genes. It causes your body to make more muscle proteins, and you get stronger.

To learn more about how teams of proteins build the body and make it work, visit Ways Proteins Make You.

APA format:

Genetic Science Learning Center. (2021, April 9) How Traits Are Made. Retrieved September 22, 2023, from

CSE format:

How Traits Are Made [Internet]. Salt Lake City (UT): Genetic Science Learning Center; 2021 [cited 2023 Sep 22] Available from

Chicago format:

Genetic Science Learning Center. "How Traits Are Made." Learn.Genetics. April 9, 2021. Accessed September 22, 2023.