The Most Dominant Genes in Humans: The Ultimate Guide

There are two kinds of genes: dominant and recessive gene. When it comes to which traits or characteristics of each individual will be visible on the outside as a result of those genes, the dominant ones will almost always prevail. I say almost, as there are specific situations in which traits of the recessive genes are visible, too, but this is beyond the scope of this post. The dominant genes are mostly expressed, which is why they also code for the more common traits or characteristics. With a little bit of a background on what these genes are, one can often predict the physical makeup of a person with reasonable accuracy, as well as the potential to have inherited a potentially life-threatening disease such as polycystic kidney disease, cystic fibrosis, sickle cell disease (affects the blood), Klinefelter syndrome (two or more X chromosomes in males), and many other recessive disorders. Here, we will give a brief overview of some of the most common dominant traits among humans through genetic inheritance. Little did you know that some of the finest traits among us are under genetic control, too.

Right-Handedness

Studies have indicated that almost 85–90% of us are right-handed. This characteristic is the result of the right-left asymmetry developmental process that also culminates in a distinction between the left and the right brain lobes. Therefore, hand preference manifests itself early in childhood as it is established before birth when dominant genes decide on it. But there is more to handedness than just which hand we prefer to eat and write with. It indicates a person’s entire motor coordination as well as brain wiring. The gene that codes for right-sided parts is PCSK6, which stands for Proprotein Convertase Subtilisin/Kexin Type 6 (and we will leave it at that).

Dark Hair

The dominant trait of dark hair is a result of pigmentation in the hair follicles. This pigment is called melanin and dark hair is, therefore, an indicator of the amount of melanin each person has as well as the number of hair follicles they have on their scalp. Genetically speaking, the more hair follicles someone has, the darker their hair will be. Nearly half of all Americans have dark hair. This is even more pronounced in other races where nearly all of the individuals have dark here. As such, the prevalence of dark hair in Black, Latino and Asian gene pools, a ratio of dark hair to other colors is as high as 2:1.

Brown Eyes

This is by far the most common dominant gene in humans, one that incredibly prominently prevails over all other colors. In fact, approximately more than half of the world’s population have brown eyes. Many children are initially born with blue eyes that eventually turn a darker color as a result of pigment darkening. Just like with hair color, this pigment is melanin, and the amount of it determines the color of a person’s eyes. I will not go into all of the genes that determine eye color but suffice to say that there are several of them that code for very specific things. These include the cells that produce melanin as well as differentiation between blue and brown eyes. Also, eye color can change based on emotions, too, as iris size is an effect of a person’s emotional state.

Free Ear Lobe

Free Ear Lobe

It is interesting to realize just how detailed the human’s outward appearance is controlled by genes. An example is the free ear lobe or one that is not directly attached to the side of the head. The genes that code for ear lobes that are not attached are dominant. Determination of this was largely based on family observations much like genetic dominance (dominant and recessive gene) was determined nearly two centuries ago. Scientists observed two sets of parents who had attached earlobes and actually had children whose ear lobes were not attached. When the children from these two families had kids themselves, all of them had earlobes that were unattached. This led them to conclude that free earlobes are a result of dominant genes.

Freckles

Freckles are not only one of the most dominant traits among humans, but they are also a result of the interplay between at least two dominant genes. These small spots on a person’s skin are due to inheritance and also a result of the amount of melanin, much like hair and eye color. Most often, freckles are coded for by the melanocortin 1 receptor (MC1R gene), whereby parents who have as little as one copy of it will most likely pass it on to their children. Freckle number is determined by variations—or alleles—of MC1R. However, freckles are also largely a result of an interplay between genes and environment. Their size, color, and pattern, for example, are influenced by environmental factors such as sun exposure that could result in more freckles to appear on the face.

Dimples

Did you know that dimples are a genetic trait as well? Not only are these widely sought-after cheek indentations genetically controlled, but they are also among the most dominant traits in humans. You may think that they are, in fact, not that common in terms of inheritance, and you are partly right. While the gene that codes for dimples is dominant, the trait is not always visible. This means that the gene is an “irregular dominant” meaning that the children of parents who have dimples will have the dominant gene but will not always express the trait. However, this is rare and unlikely and led scientists to determine that this irregularity is a result of interplay between multiple genes.

Widow’s Peak

A hairline that forms a V-shape at the center of the forehead also called a widow’s peak, is among some of the most dominant inheritance patterns among humans. However, this claim is inconclusive and warrants follow-up research to be confirmed. Some sources claim that the widow’s peak is under the control by just one gene. However, the shape of the hairline is continuous and not always obvious (i.e. some have an obvious V-shaped peak while others have a mild ‘dip’ so to say). This is why it is difficult to say that just one gene is at play. Rather, the hairline is the result of several genes. However, this warrants more research and investigation to fully confirm.

Laura Day
 

>