Rare genetic traits are features that are uncommon within the general population. They can lead to different observable features or to rare physical abilities. Rare genetic traits are typically inherited.

Genetic traits refer to specific characteristics that an individual may have. Traits may be observed, such as in hair and eye color, or whether or not you have dimples. They may also be measured, such as with height.

There are a wide variety of genetic traits out there, and some of them are rarer than others. Keep reading to discover some examples of rare genetic traits.

Simply put, rare genetic traits are those that are uncommon within the population.

These traits may lead to observable physical characteristics, such as having eyes that are different colors or having two rows of eyelashes.

Additionally, rare genetic traits may result in specific physical abilities, such as an insensitivity to pain or a resistance to HIV infection. On the flip side, some rare genetic traits may also cause or boost your risk for certain health conditions.

You generally inherit rare genetic traits from one or both of your parents. The exact pattern of inheritance can depend on the specific trait in question.

It’s important to point out that some rare traits aren’t always inherited. For example, having two different-colored eyes, called heterochromia, can also be caused by eye injuries or conditions like uveitis or eye tumors.

Here are some examples of rare genetic traits.

Heterochromia

Heterochromia is when you have two different colored irises. It can affect the whole of your iris (complete heterochromia) or just a part of one iris (partial heterochromia).

You can be born with heterochromia or acquire it later in life due to several different health conditions. The type of heterochromia that you’re born with can be inherited.

Super taste

The term supertaster refers to people whose sense of taste for certain flavors, such as bitterness, is higher than normal. These individuals have more taste buds on their tongue than non-tasters.

The term supertaster was coined in 1991 when laboratory experiments found that some people reported the chemical 6-n-propylthiouracil (PROP) to be intensely bitter.

About 25% of people in the United States are believed to be supertasters. The trait has been linked to the TAS2R38 gene.

Needing very little sleep

Researchers have identified a variant in the DEC2 gene that results in people having short sleep duration without the effects of sleep deprivation. This variant can be inherited.

Individuals with this variant have increased expression of orexin, a hormone associated with wakefulness. Research has found that those with the DEC2 variant averaged 6.5 hours of total sleep compared to 8 hours in those without it.

Sunlight sneezing

If you’ve ever walked out into the sunlight and started sneezing, you may have ACHOO syndrome. The mechanism of why this happens isn’t fully understood.

Also referred to as photic sneezing, ACHOO syndrome can be inherited in a dominant manner. If one parent has it, there’s a 50% chance that a child will have it.

Golden blood

Golden blood isn’t actually golden. It’s called this because it’s so rare. About 1 in 6 million people worldwide have golden blood.

Also called Rhnull, golden blood is a rare blood type where people have very little to no Rh antigen on their blood cells. It’s inherited in a recessive manner.

Extra rib

A cervical rib is an extra rib that forms in your neck area. Only about 0.5% to 1% of the population has a cervical rib. They’re believed to develop due to mutations in genes important for the formation of ribs.

The presence of a cervical rib increases the risk of thoracic outlet syndrome. This is where nerves around your collarbone and first rib become compressed, leading to pain, numbness, and weakness in the affected shoulder and arm.

Double eyelashes

Having two rows of eyelashes, called distichiasis, can be present from birth or occur due to other health conditions.

When present from birth, it’s often associated with lymphedema-distichiasis syndrome (LDS), which is caused by genetic changes in a gene called FOXC2.

LDS is inherited in a dominant manner. In addition to two rows of eyelashes, people with LDS also have fluid accumulation (edema) in their legs, which leads to swelling.

HIV resistance

A rare genetic change has made some individuals resistant to HIV infection. Called CCR5-∆32, this change prevents HIV from infecting immune cells.

The frequency of the CCR5-∆32 gene variant, or allele, varies across different regions. People who carry two copies of this variant, referred to as homozygous individuals, have resistance to HIV infection.

Insensitivity to pain

In rare situations, genetic variants can lead to pain insensitivity. This is caused by changes in a gene called SCN9A, which codes for a protein that’s important for feeling sensations like pain.

Feeling pain can alert us to dangers in our environment or to injuries. Because of this, individuals with pain insensitivity are at a higher risk of serious injuries.

The SCN9A variant is inherited in a recessive pattern. That means that a person needs two copies of it to be insensitive to pain.

In genetics, dominant and recessive refer to how two versions of a gene, called alleles, can interact with each other. You have two alleles of each gene, one from each of your parents. Some alleles are dominant while others are recessive.

When you inherit a dominant allele and a recessive allele, the trait of the dominant allele is expressed. In order to show a recessive trait, you need to inherit two copies of the recessive allele, one from each parent.

For example, there is a wide spectrum of eye colors. Brown eyes are dominant over blue eyes. Genetic conditions may also be inherited in a dominant and recessive manner.

The allele for cystic fibrosis is recessive, meaning two copies of the recessive allele are needed to have cystic fibrosis. Meanwhile, the allele for Huntington’s disease is dominant, meaning only one copy is needed to have it.

Traits can also be inherited or acquired. An inherited trait is passed down from one generation to the next. Examples of inherited traits include things like hair and eye color, color blindness, and genetic conditions.

Acquired traits are characteristics you develop over the course of your life. A couple of examples include a scar from a previous accident or injury, or an increase in muscle mass from lifting weights.

In some situations, an acquired trait may be inherited. DNA methylation patterns, which can influence which genes are “on” or “off,” can be influenced by environmental factors. Although more studies are needed, some research suggests these changes may sometimes be inherited.

Rare genetic traits refer to those that are uncommon within the general population. They may lead to different physical features or abilities.

There are many examples of rare genetic traits. A few that we’ve discussed include heterochromia, ACHOO syndrome, golden blood, and resistance to HIV infection.

You typically get rare genetic traits by inheriting them from one or both of your parents. The way these traits are inherited can vary based on the specific trait.