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Much of what you look like comes from a combination of your parents’ DNA. Your hair’s texture and color are no exception. Genetic information that’s embedded in your body creates a formula for what your hair is going to look like throughout your lifetime. Other factors, like nutrition, health conditions, and hormones, have less impact than the DNA that you’re born with.

If both of your parents were born with curly hair, chances are that you’ll be born with curly hair, too. But there are cases where two curly haired parents can produce a child with straight or wavy hair.

Curly hair is considered a “dominant” gene trait. Straight hair is considered “recessive.” To put that in simple terms, that means that if one parent gives you two curly haired genes and the other parent gives you a pair of straight-haired genes, you’ll be born with curly hair.

Both of your parents give you two pieces of genetic information, called alleles, that determine what your hair type will be. The two alleles from your biological father combine with two alleles from your biological mother, giving you four in all.

Typically, a dominant gene is one that overpowers a recessive gene when two different characteristics are present in one piece of DNA. The dominant gene will become the visible trait in the person born with both characteristics in their DNA. A recessive gene is a piece of genetic information that you can’t see, but that you may carry.

Let’s say that your father has curly hair. That doesn’t mean that both of his alleles are for curly hair. Since curly hair is dominant, he may have been born with curly hair but carry an allele for straight hair, too.

Let’s also say that your mother has straight hair. Maybe she inherited two alleles for straight hair. That would mean you’ve got three alleles for straight hair, and only one for curly hair. You could very well be born with straight hair, or pass the possibility of having straight hair down to your children.

There isn’t necessarily one single gene that causes your hair to become curly. Your hair type is the result of how your parent’s DNA combines, in addition to your ethnicity. Studies suggest that people with different ancestral histories have different genes that are responsible for their hair type.

There are some human traits and health conditions that are determined only by your mother’s DNA. These are called “Y-linked” factors because they’re passed through the Y chromosome.

There are also traits and conditions connected to your father’s DNA. These are called “X-linked” factors because they’re passed through the X chromosome. The way your hair looks is neither Y-linked or X-linked.

The only exception to this would be if you have a genetic health condition with symptoms that impact the way that your hair appears. In some cases, these genetic health conditions may be linked to a single gene or a single mutation within a single gene.

Being born with curly hair doesn’t mean that your hair will have that texture for the rest of your life.

Hormonal changes

Hormones can influence your hair follicle structure at different points of your life. Researchers still don’t completely understand all of the scenarios that can cause this to happen.

You may notice that your curly hair becomes thicker, heavier, or less curly during pregnancy, for example. You may see your hair become less curly if it thins out postpartum. Hormone fluctuations during menopause may also cause hair texture to change.

Environment

There’s also the matter of your immediate environment. Maybe you’ve lived in a humid climate all of your life but move to the dry, cool mountains. Your hair’s texture may look a little different with the change in altitude, humidity, and even the water you’re using to wash your hair.

Health conditions

Certain health conditions can change the way that your hair texture looks, permanently or temporarily. Alopecia can diminish the thickness of your hair, making it appear less wavy. Medications and treatments like chemotherapy can also change the look and feel of your hair.

Nutrition

Finally, there’s the food that you eat and the nutritional supplements that you take. There’s no magic food or vitamin that you can consume that will make your hair look a certain way. But pursuing and prioritizing your health by eating a varied, well-balanced diet and meeting all of your nutritional needs can make a difference in how your hair looks.

When you’re at your healthiest, your hair may look shinier, fuller, and more natural, and your hair’s texture may vary accordingly.

Curly hair is determined by factors you inherit from your biological mother and your biological father. There’s no single gene that determines the way that your hair looks. The way your hair looks when you’re born is also a clue into the genetic information you’d pass to your own children if you have them.

While your hair texture may vary throughout your life, that doesn’t mean that your DNA has changed. Factors like hormones, nutrition, and your environment can make your hair fiber appear more curly or less curly throughout your lifetime.