Red Hair, Blue Eyes and Other Genetic Mutations
It is generally believed that all human beings share approximately 98 percent of their genetic makeup. Over the centuries though, DNA has evolved, changed and mutated, so some of us bear little similarities to our ancestors in regard to things like physical features and height.
Even though many people go to great lengths to appear like everybody else, we almost all have something that makes us different from the next person. Usually it's a personality trait, some skill we know, or a talent that not many people have.
Some of us, however, have physical characteristics that make us stand out in a crowd: such as our height, complexion, or the shapes of our faces. Most of these are just a part of our genetic makeup, but some are the direct result of genetic mutations.
What Is a Genetic Mutation?
Put simply, a genetic mutation is when something in our DNA doesn't quite do what it's supposed to. People generally associate the term with birth defects and, indeed, conditions such as albinism, deformities and even some mental conditions.
Deoxyribonucleic acid, or DNA, is our genetic blueprint. It tells our cells what do do as we develop. Genetic mutations are the result of a change or a 'misfire' in our DNA. These genetic mutations are often passed down from parent to child, which is why we often resemble our parents and sometimes inherit diseases like diabetes, sickle-cell anemia, certain cancers, asthma and, sometimes, a resistance to specific diseases.
Polymorphisms are genetic changes that occur in more than one percent of the population. These are responsible for hair color, eye color and blood type. These DNA changes do not just occur in humans, but are also responsible for different traits and varieties in other species, such as the black Labrador retriever and their yellow or chocolate cousins.
It is generally accepted in the scientific world that modern homo sapiens first originated in Africa about two-hundred thousand years ago. Without genetic mutations, we would likely all bear the same dark skin, brown hair and brown eyes of our ancestors. The term usually has negative connotations, but some of the results of mutations are not harmful. It's important not to think of a genetic mutation as a defect. It's simply a change in our cellular makeup. So do not fill out your application for Xavier's School for Gifted Youngsters just yet.
The general consensus is that the first red-headed human appeared in Africa about 50,000 years ago. Soon after, people with fiery hair began migrating to Europe. But how did red hair happen in the first place?
Scientists have declared that red hair is a genetic mutation of sorts that occurs in less than three percent of the entire human population. In some areas, such as Great Britain, red hair occurs in as much as six percent of the population. It is the rarest hair color among humans and is often associated with very fair skin, light colored eyes and freckles.
The genetic culprit is the gene melanocortin 1 receptor, or MC1R. MC1R is located in the cell membrane and is affected by the pituitary gland. The pigment pheomelanin is what gives hair its red color. 50,000 years ago, a genetic anomaly occurred that caused MC1R to release more pheomelanin that normal and, viola, a redhead was born.
Red hair is referred to as a recessive gene. For a recessive trait to be inherited, both parents have to be carrying a copy of the trait in their DNA. Because both parents need to have the recessive gene to pass it on to their children, certain traits often skip at least one generation.
Blond hair is also a genetic mutation believed to have first occurred about 11,000 years ago. The color is thought to be so prevalent in certain areas of the globe, especially Europe, because of sexual selection. Since blond hair was rare and prized, people possessing it were more often chosen as mates.
All humans originally had brown eyes, which occurred because of the large amount of pigment that gives color to the eyes. Scientists believe that blue eyes first occurred between 6,000 and 10,000 years ago, and that all people with blue eyes share a single, common ancestor.
The gene OCA2 controls melanin, the pigment that gives us our coloring. Because of the mutation of an adjacent gene, HERC2, OCA2 turned itself off, like a switch, and allowed humans' eyes to turn blue or, rather, disallowed the eyes to be colored by pigment.
Blue eyes were previously thought to be a recessive gene, but that theory has been proven incorrect. If one parent has blue eyes and the other has brown, the resulting children will generally, but not always, have brown eyes as they are the more dominant trait. Also, two brown-eyed parents can produce a child with an eye color other than brown, even if there are no ancestors with blue or green eyes.
OCA2 is also responsible for albinism: when it is completely turned off, people are born with no pigment in their eyes, skin or hair.
Green eyes are actually a form of brown eyes caused by the amount of melanin that is found in the iris, while Amber eyes are a result of extra yellow-colored pigment in the iris and Grey eyes are caused by deposits of collagen in the iris. Hazel eyes are caused by the amount of melanin in the iris and are affected by Rayleigh scattering, which allows the color to shift in certain lights.
Though Elizabeth Taylor's beautiful eyes were considered to be violet and were one of her largest claims to fame, they were actually a shade of blue. Violet, purple and red eyes can only occur with albinism.
A fairly rare eye color condition, heterochromia iridium, allows for each eye to become a different color. This does not only occur in humans, but also in animals. Husky dogs, for example, often have two different colored eyes. This condition, usually caused by a genetic mutation, can also be inherited. The other causes of Heterochromia are disease and injury. A variation of this condition, sectoral heterochromia, causes some to have multiple colors in the same eye.
Are you a mutant?
So, Are We Mutants or Just Different?
Gingers get picked on, often called carrot tops, and sometimes kids offer to connect the dots of their freckles. There are millions of "dumb blond" jokes too, and some people are creeped out by people with multi-colored eyes. People who have these differences often wish they didn't, while those who don't have them often wish they did.
It is true that some of these physical features are caused by genetic mutations, but, in the end, these are just some of the things that make us different. The world would be a very boring place if we all looked exactly alike. After all, variety is the spice of life.
Interesting Scientific Video about Genetic Mutations
Questions & Answers
© 2012 GH Price