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What are Traits?
Updated on February 19, 2024
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What are Traits?

A trait is a specific characteristic found in an individual. It can be something physical and immediately observable, such as eye color, skin color, or hair color, or something more internal, like the ability to roll one’s tongue or cross the eyes.

What Are Traits Determined By?

Traits are predominantly determined by the following:

  • Genetic factors
  • Environmental factors
  • A combination of both

However, many other factors can affect your traits.

While many of your traits are inherited (such as physical traits and even some behavioral ones like neuroticism and openness), they can be heavily influenced by your environment, upbringing, and even exposure to harmful toxins while you're growing up.

Not only that, but the people you are surrounded by, the community you grow up in, and even the culture you're brought up in can impact your traits.

For example, if you're more extroverted and outspoken due to your genes, but you grow up in a very conservative area that attempts to "tone you down" due to some religious or cultural belief, that extroversion may be dulled.

Conversely, if you have a predisposition to anxiety and depression but are raised in a very supportive, loving family, it may not manifest as strongly.

So while you may inherit certain traits, there's no guarantee they will manifest. In short, your traits and how they are expressed arise from a complicated overlap of several different factors. Physical traits may be the easiest to retain, but even those can mold and change.

What Are Traits, Genes, and Alleles?

These three terms are often confused with each other. While they're related, they all pertain to different things.

While often interchanged, genes, alleles, and traits all differ from each other. Here are their definitions:

  • Genes – Genes are part of the DNA sequence and contain information contributing to a living organism’s genetic makeup. A gene is what houses genetic instructions and contains information.
  • Alleles – The term "allele" is often used when talking about the variant of a specific gene. An allele is a version of a gene or the form that a gene's instructions can take.
  • Traits – A trait is a characteristic or feature identifiable because of a living organism’s genes. If it's a physical characteristic, it's observable. If it's a personality trait or something inherent, others may have noticed it. It's the result of the specific allele's expression.

Think of it like this: genes provide the blueprint, that specific blueprint in that gene is the allele, while traits are what are made out of those blueprints. As the outcome of your genetic makeup, traits are what can be observed. Without the varaint of a gene (the allele), you do not have traits.

If you're still confused, the term "gene" is often the more general term used. "Allele" is used when pertaining specifically to a gene that is supposed to carry what will become a specific trait.

So, in terms of physical traits like hair color, this is what it would look like: The gene houses the information, the allele is the version of the gene that contains curly hair instrctions, and the trait is the curly hair itself that people can observe.

It's most obvious with physical traits, but behavioral traits can also work this way to an extent.

Dominant vs. Recessive Traits

The expression of traits depends heavily on the alleles that an offspring inherits.

Alleles are versions of genetic sequences. Every offspring’s genes are made up of one allele from each parent. A gene is made up of two alleles. This pair is made up of one allele from the mother and one from the father.

Alleles can be dominant or recessive within a pair. For example, between physical traits like brown eyes and blue eyes, brown eyes are the more dominant trait.

What are Traits? 7

Suppose the allele pair has either dominant alleles or just one dominant allele and one recessive; the dominant trait is expressed. Dominant traits are always expressed even if there’s only one dominant allele.3

It’s only when two recessive alleles are in a gene that the recessive trait is expressed. Recessive traits manifest due to the absence of a dominant one.

Dominant alleles are usually denoted by capital letters, while recessive ones are denoted by non-capital letters when it comes to visual genetic representations, like punnet squares. For example, the brown eye allele is often denoted as "R" while the blue eye allele is "r."

However, remember that, in some cases, dominant traits aren't dominant in all pairs. Some dominant traits may not be dominant when paired with others, nor are they the only dominant trait.

Common Dominant and Recessive Pairs

Some of the most common dominant-recessive trait pairs in physical traits are (dominant on the left, recessive on the right):

  • Dark hair vs. light hair
  • Brown eyes vs. blue eyes
  • Curly hair vs. straight hair
  • Ability to roll the tongue vs. cannot roll tongue
  • Detached earlobes vs. attached earlobes

How Are Some Alleles Dominant and Some Recessive?

There are several theories as to why some alleles have evolved to become more dominant and others more recessive.

Some pepople believe that natural selection has genetically empowered certain traits to protect our species and minimized the chances of us inheriting recessive traits, which may be considered less valuable to survival.4

Genes that are considered important for survival and reproduction are often prioritized. "Harmful" genes have become more recessive due to evolution. This theory makes sense when you think of how many (but not all) harmful genetic variants are often recessive.

This goes for both physical traits, behavioral traits, and even other genetic predispositions.

Will Dominant Alleles Always Show?

While dominant trait expression is what usually happens, there are many things that can affect that. Some factors include:

  • The interplay of other genes and traits
  • Interruption from toxic external factors (like drugs, toxins, pollution, etc.)
  • Incomplete penetrance or when a gene only expresses some of the traits associated with it

Remember that trait inheritance isn't that simple. Just because you inherit a dominant trait doesn't mean that factors surrounding its expression will also be smooth sailing. Sometimes there are other genetic mutations around that dominant trait, a complex combination of traits, or even external factors that can affect its manifestation.

What Happens When You Inherit Two Different Dominant Traits?

If, for example, you inherit two dominant traits that are completely different, you may experience codominance. Codominance is when both traits are expressed without masking one another.

For example, the AB blood type is a combination of dominant blood type A and dominant blood type B.

What are Traits? 8

Other times, the two traits blend together as neither is masked.

You can observe this in many flowers. If a white flower and a red flower cross-pollinate, it's not always guaranteed that they will be either white or red. In some cases, if the traits are codominant, the offspring will be pink or even be splotches of red and white. This is how people who cultivate flowers are able to develop specific colors.

History Behind Traits

Austrian biologist Gregor Mendel famously grew peas in his abbey’s garden. He began to take note of the traits and features he noticed were passed down to offspring plants after cross-pollination.1

By identifying different traits to pinpoint in each plant and its offspring, he proved that specific traits are dominant and are more likely to be passed down to offspring in every generation.

In contrast, others are recessive and have a smaller chance of manifesting in the next generation, only to become present in the subsequent generation.

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The first offspring in Mendel’s experiment all exhibited the dominant trait. After allowing these offspring to self-fertilize, the new generation revealed the “hidden trait,” proving that traits that aren’t necessarily observable don’t just disappear in the gene pool.

Offspring that inherit two recessive traits will exhibit the “hidden trait.” As long as a dominant gene is present, a recessive trait will not manifest.

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Mendel’s study paved the way for genetics today, making him the “father of modern genetics.”

Types of Traits

There are two types of traits:

  • Genetic or inherited
  • Behavioral or learned

Traits can be inherited (genetic) or learned (behavioral).

Traits like freckles, widow’s peaks, or eye color are inherited. Other traits come about via external influence, like loss of limb during an injury or bodily changes from committed exercise.

Behavioral characteristics or traits, like animals’ defense mechanisms, are usually shaped by the environment they’re in.2

Traits that are acquired but further developed by genetic influence are also possible.

For example, a tennis prodigy may give birth to a child who is also talented at tennis, but not because they inherited the expertise. Maybe their parent’s athletic disposition that lent itself to proficiency was passed down to their child, who just so happened to be able to apply it to tennis.

What are Traits? 11

Physical traits are easier to spot than dispositions and behavioral traits offspring may have inherited. Behavioral traits are also shaped by the environment, a reason for many debates about nature vs. nurture in shaping a child’s personality.

Can an Inherited Trait Fail to Express?

Yes, it's possible for traits you inherit not to manifest. This is because of several factors, environmental factors being one of them.

It's important to note that trait expression doesn't isn't necessarily a black-and-white situation. Gene expression is more like a spectrum, with different levels or "intensities" of a trait being expressed.

So rather than an on or off switch for whether or not a trait will manifest, it may just not be as loud or noticeable as others in some while very noticeable in others.

For example, in a family that has curly hair, some may have more tightly coiled hair while others will have looser waves.

Other reasons traits may not be expressed are:

  • Harmful factors from someone's environment, such as toxins, drugs, stress, and poor lifestyle choices
  • Incomplete penetrance, where you don't exhibit any or all traits of a gene you inherit
  • Variable penetrance, where you only display certain aspects of a trait you inherit, as it exists on more of a spectrum
  • "Skipped" a generation or the trait was recessive and was paired with a dominant one, keeping it "hidden"

While you may have inherited a trait, there's no guarantee it will be expressed. Genetics and the traits you inherit result from a complex interplay of different factors, genetic, environmental, and many more.

How Are Traits Passed Down?

When parents have children, their genetic information is combined to create a unique new DNA structure in their offspring, which makes their children unique but with familiar features. This makes up their characteristics.

Parents contribute two alleles to each offspring’s genes. Certain features are expressed over others as traits depending on whether those alleles are dominant or recessive.

For example, if the father has curly hair, and it’s the dominant allele, and it gets passed down to a couple’s children, it will be more likely that the child will come out with curly hair even if their mother has straight hair.

A child can inherit different traits from their parents. You may have your mother’s eyes but your father’s disposition, etc.

Behavioral characteristics can also be passed down in a similar way, though a lot of personality and behavior can be more heavily impacted by enivironment.

Do People Who Share Genes Share the Same Traits?

People who share the same genes may share and exhibit similar traits—though they won't share all of them. Siblings will often have similar features or even dispositions, and some identical twins may also have similar personalities.

However, note that just because you share a substantial chunk of your genes, you won't be completely similar. Not even identical twins are totally alike. This is because, despite having similar genes, your genetic sequences may still be totally different and manifest completely different traits.

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Each person has a unique set of genes, and these genes carry a unique set of traits.

Certain traits will be expressed over others and sometimes in varying degrees. For example, parents who pass curly hair to their children may observe that not all their children’s curl types will be the same. A child may even express the straight hair trait altogether.

Updated on February 19, 2024
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4 sources cited
Updated on February 19, 2024
  1. Gregor Mendel Pea Experiment.” Michigan Gov.

  2. Traits.” Biology Online Dictionary.

  3. Explore The Difference Between Dominant and Recessive Traits.” BYJU’S.

  4. "Gene expression drives the evolution of dominance." Nature Communications.

Angela Natividad
Angela Natividad
Content Contributor
Angela is a full-time digital content manager and editor for Know Your DNA. She also contributes freelance articles to several local and international websites when she has the time. She's always been a voracious believer in finding the truth and ensuring the science is sound.
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