Genetics of Hair Color

Know Your Health: Genetics of Hair Color

By LunaDNA Contributor

Hair colors are passed down through generations. Sometimes the colors are predictable, and sometimes, unexpected colors occur through a genetic mutation. Learn about the genetics of hair color. 

Hair colors are a spectrum of hues that can range from white blond to coal black. Hair color is inherited, and many genes are involved in the process. Sometimes, unexpected hair color can occur in a child because of a genetic mutation. Some of the genes involved in hair color also influence eye color and skin color.  

Hair color is the result of genetics. Learn about the genetics of hair color and what causes different hair colors in this guide.  

  • How is Hair Color Determined? 
  • Is Hair Color Genetic? 
  • Is Hair Color Inherited? 
  • Can Hair Color Be Predicted? 
  • What Does Your Hair Color Mean?  
  • Brown Hair 
  • Black Hair 
  • Blond Hair 
  • Red Hair 

How Is Hair Color Determined? 

Two types of pigment, or melanin, determine hair color. An abundance of eumelanin colors hair black or brown, and an abundance of pheomelanin colors hair orange or red. Every hair color contains some amount of the darker pigment eumelanin. Low levels of eumelanin result in lighter hair, and higher levels result in darker hair.  

The genes responsible for hair color are neither dominant nor recessive — it is a matter of which genes are turned on or turned off. The hair color produced depends on the amount and type of melanin produced by melanocytes (melanin-forming cells). If receptors on the surface of the melanocytes are active, they produce, eumelanin, the pigment responsible for brown or black hair. If the receptors are inactive or blocked, they produce pheomelanin, the pigment responsible for orange or red hair.  

Jet-black hair has large numbers of tightly packed eumelanin. Red hair has large numbers of tightly packed pheomelanin. Blonde hair has both types of melanin, but in very small amounts and loosely packed. Variations lead to a wide range of shades within each hue. Hair color usually darkens as genes are turned on and off during childhood and puberty. Later in life, hair can turn gray and white as fewer pigment cells produce and store melanin. Gray hair has only a little pigment in it, while white hair has no pigment. 

Is Hair Color Genetic? 

Hair color is one of several physical traits that are genetic, or passed down through an individual’s DNA. Human DNA has millions of on and off switches along networks that control how genes function. Genes responsible for hair color come from both parents.  

Although the genes passed down from a child’s parents determine hair color, variations can result in a child having a different hair color than both parents. The genetics of hair color is the result of many genes working together to control the amount and type of melanin. Large amounts of very dense eumelanin produce black hair. Moderate somewhat dense amounts result in brown hair. Very little and thinly dispersed amounts result in blonde hair. If you have mostly pheomelanin with a little eumelanin, red hair is the result. Additionally, a variation in the blond gene can lead to premature graying.  

Is Hair Color Inherited from Mother or Father? 

Hair color comes from both parents through the chromosomes passed onto their child. The 46 chromosomes (23 from each parent) have genes made up of DNA with instructions of what traits a child will inherit. The results can be surprising. For example, black-haired parents can unknowingly each carry an unexpressed blond-hair gene that can pass to their fair-haired child. This explains why siblings can have different shades of hair.  

What Does Your Hair Color Mean? 

Hair color may be related to your ancestry. Darker hair is more prevalent among people in the southern hemisphere, and lighter hair is more common in the northern hemisphere. Darker hair is associated with areas of harsh sunlight, and lighter hair with areas of less sunshine. However, there are many exceptions due to genetics, migration of people, and other factors. 

Black and Brown Hair 

The most common hair colors around the world are black and brown, and it is estimated that over 90 percent of people have black or brown hair. Depending on the levels of pigment, colors range from an almost light-blond brown to dark black.  

Blonde Hair 

Blonde hair is produced by low levels of pigment (called eumelanin). Variation in the small amounts of eumelanin accounts for the wide range of blond shades, from platinum blond to dark golden blond. Many people with blond hair develop darker hair later in life. Natural light blond hair in adults is rare.  

Red Hair 

Red is the rarest hair color and is thought to be found in around 1 to 2 percent of people worldwide. In the Northern Hemisphere, 2 to 6 percent of people have red hair.  

Red hair ranges from light strawberry blond to deep burgundy, depending on the amount of pheomelanin (red pigment) and eumelanin (brown/black pigment) is present. Auburn hair has a higher concentration of pheomelanin, while chestnut hair has more eumelanin.  

Red hair has fascinated humans throughout history. In fact, the term “redhead” was first noted in the 16th century. In addition, frescos from ancient times depict Hades, the god of the underworld, as a redhead.  

Over time, scientific discoveries have led to a deeper understanding of the genetics that affects hair color. As advancements in genetics and overall health are made, more discoveries will undoubtedly unlock the mysteries of who we are, where we’re from, and why people around the world come in so many shapes, sizes, and hair colors. 

LunaDNA is bringing together people and researchers to better understand life, including genetic traits like hair color. Directly drive health discovery by joining the All About Me Study. The more people who come together to contribute health data for the greater good, the quicker and more efficient research will scale, and improve the quality of life for us all.  

Click here to get started.

Are Crooked Teeth Genetic?

Know Your Health: How Your DNA May Affect Your Smile

By LunaDNA Contributor

The causes of crooked teeth are varied. Our ancestry may have interesting clues to the genetics of crooked teeth. Learn about crooked teeth, and how DNA may play a role in overall teeth health. 

According to the American Association of Orthodontists, an estimated 4 million people wear braces on their teeth. However, misaligned teeth are a recent development in human evolution. Early human fossils from cavemen usually have well-aligned, uniform teeth. Some anthropologists believe the development of misaligned teeth occurred when our jaws began shrinking over time due to changes in our diet that required less chewing. Today, we know that some genetic factors, such as jaw size and number of teeth, can affect misalignment, but behaviors and environmental causes are also involved.  

Are Crooked Teeth Genetic?

Crooked teeth are common over the last few hundred years, yet skulls from humans that lived thousands of years ago have well-aligned teeth. Fossils show that cavemen didn’t have many dental problems despite the lack of toothpaste and floss. Today, dental consultations are recommended before the age of 8. Learn more about crooked teeth and its genetic connections, including:  

  • What Causes Crooked Teeth? 
  • Types of Crooked Teeth 
  • Are Crooked Teeth Genetic? 
  • Ancestry of Crooked Teeth 
  • Problems Associated With Crooked Teeth 
  • How to Fix Crooked Teeth 

What Causes Crooked Teeth? 

Crooked teeth do not always happen by chance. Habits and maladies that may lead to undeveloped jaws and crowded teeth include

  • tongue thrusting (also known as reverse swallowing) 
  • thumb sucking 
  • prolonged use of pacifiers 
  • mouth breathing (due to allergies, asthma, and other conditions that cause a person to breath through his or her mouth) 
  • open mouth posture 
  • tumors of the mouth and jaw 

These habits and maladies contribute to poor jaw growth, leaving many with misaligned teeth and undeveloped jaws. This improper development can limit the space available for teeth and can prohibit them from growing in the ideal position.  

An undeveloped jaw can lead to a mouth of crowded teeth. Since orthodontia work does not usually start until all permanent teeth come in, teeth might be pulled, because the jaw is deemed too small to accommodate all the teeth.  

Mouth breathing leads to the tongue not resting in the correct position on the roof of the mouth. This can in turn lead to an underdeveloped upper and lower jaw. An upper jaw improperly developed may restrict the airway further. This can keep the mouth open, which might exacerbate the problem.  

Reverse swallowing, also known as tongue thrusting, occurs when the tongue pushes forward and the lips push back when swallowing. A child swallows at least a couple times a minute, so pushing the tongue forward against the teeth can, over time, create a condition called open bite.  

Diet may be a factor too. In the 1930s, Weston Price, an American dentist, studied various groups around the world and found that those employing a primitive diet had little tooth decay, larger jaws, and straight teeth. Orthodontics became a specialty in 1900 in response to bad habits and maladies that children had during the Industrial Revolution. After the Industrial Revolution, people swapped out a natural diet, closer to what their ancestors had eaten, for one of more processed foods. It is possible that this softer diet hindered normal jaw growth because less jaw strength was required.  

Types of Crooked Teeth  

Crooked mouthfuls of teeth come in all shapes and sizes, but there are three general classes of malocclusions, which means misaligned teeth:  

Class 1 occurs when the upper teeth slightly overlap the lower teeth, but the bite is normal. This is the most common type of crooked teeth.  

Class 2 occurs when the upper teeth and jaw severely overlap the lower teeth and jaw and is sometimes called an overbite. Difficulties in chewing can be painful and can lead to headaches and temporomandibular joint dysfunction (TMJ), a painful condition of the joint that connects your jaw to the side of your head.  

Class 3 occurs when the lower teeth project beyond the front of the upper teeth when the jaw closes and is sometimes called an underbite. Those with underbites can have trouble chewing and often suffer from headaches. Overtime, an underbite can cause TMJ.  

Are Crooked Teeth Genetic? 

Humans today are nearly identical to their ancestors who had straight teeth. This suggests that crooked teeth are partly a result of evolution. Some experts believe that the Industrial Revolution, which happened about 150 to 200 hundred years ago, triggered people to have crooked teeth.  

Interestingly, most wild mammals have straight teeth. Some researchers believe that when culture shifted from rural to manufacturing, something went awry. Others think it happened thousands of years earlier, when humans transitioned from hunting and gathering to farming. Ancestral upper and lower jaws of hunter-gatherers were more often better aligned than those of later humans. 

Ancestry of Crooked Teeth 

With the introduction of the modern baby bottle in the mid-1800s, human populations became less reliant on breastfeeding their young. Research has shown that the muscles required for an infant to breastfeed are not used as extensively when a child is bottle-fed. At the end of the 1940s, German dental experts Dr. Wilhelm Balters and Dr. Adolf Müller discovered that babies who had been breastfed had significantly fewer crooked teeth. Studies continue to be conducted to determine if there is a link between the use of bottles and the impact it has on jaw development and crooked teeth.  

Problems Associated With Crooked Teeth 

Crooked teeth make it harder to chew and can put a strain on the jaw, increasing the risk of breaking a tooth. It is also harder to clean crooked teeth, leaving the opening for cavities and other dental maladies. Protruding teeth can rub against and wear down other teeth.  

Beyond this, crooked teeth can impact overall health. This decreases the chance of bacteria going into the pockets of the gums, which can lead to gum disease. Some research suggests that, when bacteria is left untreated, it can enter the bloodstream and may lead to heart disease, diabetes, or stroke.  

While we know some genetic causes for tooth issues, much is still unknown about the connections between genes and dental problems. Researchers are hopeful that recent discoveries will open the door for the development of new and improved dental- and orthodontic-care tactics and treatments.  

LunaDNA is bringing together people and researchers to better understand life, including genetic conditions like crooked teeth. Directly drive health discovery by joining the All About Me Study. The more people who come together to contribute health data for the greater good, the quicker and more efficient research will scale, and improve the quality of life for us all.  

Click here to get started.

Is Eye Color Genetic?

Is Eye Color Genetic? | What Your Eye Color Has to Do With Your History

Eye colors are passed down through generations, but sometimes genetic variations can lead to surprising results in eye colors. Learn about the genetics of eye color in this guide.

Whether eyes are blue or brown, eye color is determined by genetic traits handed down to children from their parents. A parent’s genetic makeup determines the amount of pigment, or melanin, in the iris of the his or her child’s eye. With high levels of brown melanin, the eyes look brown. With minimal levels of the same brown melanin, the eyes look blue. However, a genetic variation can cause a child’s eye color to be unpredictable, resulting in two blue-eyed parents having a brown-eyed child.

Know Your Health: Genetics of Eye Color

Eye colors have evolved over time and have roots in our ancestry. Although eye color is determined by genetic makeup, variations can cause different shades to appear. Learn more about the genetics of eye color, including:

  • How is Eye Color Determined?
    • Is Eye Color Genetic?
    • Is Eye Color Inherited?
    • Can Eye Color Be Predicted?
  • What Does Your Eye Color Mean?
    • Brown Eyes
    • Blue Eyes
    • Green Eyes
    • Hazel Eyes
  • How Does Your Eye Health Impact Your Life?

How Is Eye Color Determined?

Genetic makeup determines the amount of melanin in the eye. In eye color, there isn’t blue or green pigment. All eye colors have the same brown melanin incapable of refracting light. The difference in eye colors is due to the concentration and location of the brown melanin on the two layers of the iris. People with brown eyes have melanin on the back layer of the iris and some on the front layer, which absorbs more light and causes the iris to look brown. Eyes with no melanin on the front layer of the iris scatter light so that more blue light reflects out, so that the eyes appear blue.

The chromosomes a child inherits carry genetic information that determines eye color. Differences in the copies received from each parent causes variations in the amount of melanin produced. A region on chromosome 15 has a big part in determining eye color. The OCA2 and HERC2 genes are located in this region.

The OCA2 gene (formerly called the P gene) provides instructions for producing the P protein located in the melanocytes (specialized cells that produce melanin). If more protein is produced, then the eyes received more melanin, and eye color leans toward the brown end of the color spectrum. When less protein is produced, the eyes receive less melanin and eye color leans toward the blue end of the spectrum. Although nearly 75 percent of eye color is controlled by the OCA2 gene, other genes provide a pathway for melanin. These genes can raise or lower melanin levels, causing a child to have more or less melanin than either parent. These variations can result in blue-eyed parents having a brown-eyed child, or brown-eyed parents having a blue-eyed child. The former is more likely than the latter.

Is Eye Color Genetic?

Each cell in the human body normally contains 23 pairs of chromosomes. Chromosome 15 likely contains 600 to 700 genes integral to producing proteins. Two of these genes, OCA2 and HERC2, play a significant role in eye color selection.

Although the OCA2 gene produces the protein responsible for melanin, the HERC2 gene controls the OCA2 gene by turning its protein production on and off. The presence of at least one genetic variation in the HERC2 gene can reduce the amount of melanin produced, leading to lighter eyes. Other genes working with OCA2 and HERC2 have a smaller role, but on rare occasions override OCA2 to determine eye color.

Is Eye Color Inherited?

Eye color was once thought to be the result of a single hereditary trait. It was thought that each person received one eye color gene from each parent, and the dominant gene determined eye color. In this model, the brown-eye color gene was always dominant over the blue-eye color gene, and only two blue-eye color genes could color eyes blue.

Charles and Gertrude Davenport developed the dominant brown eye model in 1907. They suggested that blue eyes were caused by a single recessive gene, and blue-eyed parents could never produce a brown-eyed child. Dominant and recessive genes refer to inheritance patterns, and describe how likely it is for a certain trait to pass from parent to offspring.

Today, we know this model is simplistic, and that many genes determine that eye color. Although we can predict the color of a child’s eyes based on the parent’s eye colors, other genetic factors may alter the outcome.

Can Eye Color Be Predicted?

While it is possible to predict the probability of eye color, genetic factors may alter the outcome. Movie star Elizabeth Taylor’s parents probably did not predict their daughter’s rare violet eyes. Taylor’s eye color is thought to be the result of a genetic mutation in the FOXC2 gene, which causes a specific amount of melanin that produced a striking eye color and may cause double eye lashes as well as heart problems.

With eye color controlled by more than one gene, it is possible for a newborn to inherit any eye color. Predicting eye color is further complicated because it sometimes changes after birth. A baby’s blue eyes can turn brown as more melanin is deposited into the iris over the first three years of life.

What Does Your Eye Color Mean?

According to one theory, almost everyone (99.5 percent) with blue eyes might be able to trace their ancestry back to the same blue-eyed ancestor that lived in the northwest part of the Black Sea region some 6,000 to 10,000 years ago. This is based on the DNA analysis of about 800 blue-eyed people, in which only one person did not have the same blue-eye genetic mutation as the rest of the group. This mutation seems to have occurred during the Neolithic period (or New Stone Age) during the great agricultural migration to the northern part of Europe. Nearly all blue-eyed humans have this same mutation in the same location in their DNA. By contrast, brown-eyed humans have more variation in their DNA when it comes to eye color.

Brown Eyes

The majority of people in the world have brown eyes. The color brown is a result of a high concentration of melanin in the iris causing more light to be absorbed and less light to be reflected. Because of this, brown eyes are more naturally protected from the sun. This likely had evolutionary benefits similar to darker skin being able to withstand the hot sun longer. The genes responsible for skin color are closely linked to those that cause eye color.

Though brown eyes are the most common genetic eye color, there is more genetic variation among those with brown eyes than those with blue eyes. This may account for the variations of brown eye colors. These variations come from different genes on different chromosomes that carry genetic eye color information from our ancestors.

Blue Eyes

Originally, all humans had brown eyes. Some 6,000 to 10,000 years ago, a genetic mutation affecting one gene turned off the ability to produce enough melanin to color eyes brown causing blue eyes. This mutation arose in the OCA2 gene, the main gene responsible for determining eye color. Since blue eyes have survived throughout many generations, researchers think there may have been some evolutionary benefit, though the exact reason is unknown.

Blue eyes are the result of low concentrations of brown melanin, not blue pigmentation. Less melanin allows more light to reflect back to wavelengths on the blue color spectrum, which in turn make eyes appear blue. The reason why eyes are blue is the same reason the sky is blue. Some 8 to 10 percent of humans worldwide have blue eyes.

Green Eyes

Only about 2 percent of the world’s population has green eyes. Green eyes are a genetic mutation that produces low levels of melanin, but more than blue eyes. As in blue eyes, there is no green pigment. Instead, because of the lack of melanin in the iris, more light scatters out, which make the eyes appear green. Changes in light make lighter eyes look like they are changing colors like a chameleon.

Hazel Eyes

Hazel eyes are sometimes mistaken for green or brown eyes. They are not as rare as green eyes, but are rarer than blue eyes. Only about 5 percent of the population worldwide has the hazel eye genetic mutation. After brown eyes, they have the most melanin. . The combination of having less melanin (as with green eyes) and a lot of melanin (like brown eyes) make this eye color unique.

The color combinations in shades of green, brown, and gold are endless with hazel eyes, depending on the concentration of melanin. The light scatters as it does with blue and green eyes.  As with blue and green eyes, hazel eyes may appear to shift colors depending on the light. The eye color doesn’t actually shift, perception does. It is unknown if hazel eyes developed from brown eyes or green.

How does your eye health impact your life?

Your eye health may significantly impact your everyday life, from socializing with friends to driving at night. Share your eye health experiences to help scientists better understand your eyes’ impact on your daily life. Get started here.