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In 2003, after 13 years of research, an international team of scientists working on the revolutionary Human Genome Project shared their groundbreaking results. For the first time, they mapped out the genetic components that form humans, providing researchers with 'fundamental information about the human blueprint,' as described on the project's official website. It is now known that humans possess between 20,000 and 25,000 genes, but much remains to be discovered about these tiny DNA segments. Below, we've compiled several facts regarding gene expression, genetic disorders, and how genes contribute to our identity.
The term gene wasn’t introduced until the 20th century.
Though 'father of genetics' Gregor Mendel conducted his pea plant experiments in the mid-1800s, it wasn’t until 1909 that Danish botanist Wilhelm Johannsen first identified Mendel's distinct hereditary units, which he named genes—a term derived from pangenesis, a theory of heredity proposed by Charles Darwin, which is now considered disproven. Among other ideas, Darwin suggested that acquired traits could be passed down through generations.
At the genetic level, humans are over 99 percent identical.
Humans share far more in common than we might think. Over 99 percent of our genes are identical from one individual to another. This means the differences we see among humans—such as eye color, height, and blood type—are due to genetic variations that make up less than 1 percent of our genetic makeup. These differences arise from variations of the same gene, known as alleles.
Genes can fade or become nonfunctional as species evolve.
Due to genetic factors, most mammals can naturally produce their own Vitamin C. However, somewhere along human history, we lost this ability when one of the necessary genes stopped working. 'You can observe this in our genome; half of the gene is missing,' said Dr. Michael Jensen-Seaman, a genetics researcher and associate professor at Duquesne University in Pittsburgh, in an interview with Mytour in 2019. 'Typically, when a species loses a gene through evolution, it's because it no longer needs it. If it's not necessary, it disappears. Our ancestors probably consumed so much fruit that there was never a need to produce our own Vitamin C.' Dr. Jensen-Seaman also pointed out that humans lost hundreds of odorant receptors—proteins that help detect smells—because we rely more on vision, which explains why our sense of smell is weaker compared to many other animals.
The strikingly long eyelashes of Elizabeth Taylor were likely the result of a genetic mutation.
A mutation in the aptly named FOXC2 gene gave the legendary Hollywood star Elizabeth Taylor two rows of eyelashes. This rare condition is called distichiasis, and while it may appear to be a desirable trait, there can be complications. According to the Cleveland Clinic, many people with an extra set of lashes won’t require treatment, but in some cases, the lashes must be removed to avoid potential damage to the eyes.
Genes that are involved in sperm production are among the fastest evolving genes in the animal kingdom.
Across much of the natural world, genes known as sperm competition genes are becoming increasingly adept at fertilizing eggs. This is evident in various species, including certain primates and marine invertebrates. Take, for example, the promiscuous primates like chimpanzees, where females mate with multiple males in a short span. This creates a genetic competition among males—through their sperm—to sire offspring. 'What we believe is happening is an arms race among genes involved in sperm production or male reproduction in general,' said Jensen-Seaman. Essentially, the proteins from these genes are evolving to help males rise to the occasion.
A 'zombie gene' in elephants may hold the key to protecting them from cancer.
In a 2018 study published in Cell Reports, researchers from the University of Chicago discovered that a cancer-suppressing gene, once considered 'dead' (non-functional), was reactivated in elephants. Although the reason behind this reactivation remains unclear, this 'zombie gene' might explain why elephants have such low cancer rates—just 5 percent of them succumb to the disease, compared to 11 to 25 percent in humans. Some have proposed that a drug could potentially be developed to mimic this gene's function in humans for cancer treatment.
Octopuses have the ability to edit their own genes.
Cephalopods such as squids, cuttlefish, and octopuses are incredibly intelligent and crafty, capable of rewriting the genetic code within their neurons. Unlike the typical scenario where one gene codes for one protein, a process called recoding enables an octopus gene to generate multiple proteins. Scientists found that this process helps some Antarctic species 'keep their nerves firing in frigid waters,' as The Washington Post notes.
The plot of the 1986 film The Fly isn’t entirely far-fetched.
In The Fly, Jeff Goldblum’s character undergoes a transformation into a fly-like creature after a failed experiment. Surprisingly, this idea isn’t as absurd as it sounds—at least genetically speaking. Research indicates that humans share approximately 52 percent of their genes with fruit flies, and the same estimate applies to house flies as well.
Could Jeff Goldblum theoretically become a human-fly hybrid if his DNA were mixed with that of a fly in a futuristic teleportation device? Not exactly, but there are some scientific parallels. 'With genetic engineering, we can choose specific genes and insert them into the genomes of other organisms,' explained DNA researcher Erica Zahnle to the Chicago Tribune. 'This is something we do routinely. For instance, there is currently a hybrid tomato that has a fish gene in it.'
Our genes may limit our lifespan to a maximum of 125 years.
Despite advancements in medicine, there could be a biological limit to how long humans can live. Several studies suggest that we've already reached our maximum lifespan, with the upper boundary being between 115 and 125 years. This theory proposes that cells can only replicate a certain number of times and often incur damage as we age. Even with potential gene therapy, we likely can't alter our genes quickly enough to extend life significantly, as noted by Judith Campisi from the Buck Institute for Research on Aging in an interview with The Atlantic.
As stated in a 2017 study published in Frontiers in Physiology, it's unrealistic to expect humans to live 200–500 years in the near future due to medical or scientific breakthroughs, or that we’ll be adding over a year to our life expectancy each year. This sentiment echoes previous studies from 2003 and 2010. The authors argued that raising false hopes by ignoring the fact that humans are already 'extremely optimized' for lifespan is misleading.
The notion that a single gene determines whether you have attached or unattached earlobes is a myth.
Forget what you were taught in middle school about earlobes and genetics. While genes do play a role in whether you have attached or unattached earlobes (previously thought to be a dominant trait), the idea that this characteristic is controlled by a single gene is false. Additionally, earlobes don't fit into just two categories; there's a third type, which University of Delaware associate professor John H. McDonald refers to as intermediate earlobes. 'It seems to me that there is continuous variation in the attachment height,' McDonald writes on his website. A better example of a trait determined by a single gene is blood type, which is influenced by three variations—or alleles—of one gene, according to Jensen-Seaman.
No, there isn’t a 'wanderlust gene' or 'music gene.'
Occasionally, new studies emerge suggesting a genetic basis for traits like personality, preferences, or skills. In 2015, there was talk of a 'wanderlust gene' driving some individuals to travel, while other reports proposed that musical talent might be inherited. However, the reality is more complex. 'The problem is, when we’re in school, we learn about traits governed by a single gene, like Mendel’s peas, and we begin to think all variations must be due to one gene,' explained Jensen-Seaman. 'But aside from rare genetic disorders, most of what interests us in medicine, human behavior, or variation are 'complex traits.' These traits usually involve hundreds, if not thousands, of genes, in addition to environmental factors throughout life.
DNA testing kits can’t tell how smart you are.
Like your abilities and personality, intelligence is a complex trait that’s difficult to quantify because it’s influenced by numerous genes. A 2017 study identified 52 genes linked to higher or lower intelligence, but these genes have a predictive power of less than 5 percent. In 2018, another study pinpointed 538 genes tied to intelligence, with a mere 7 percent predictive power. In short, no DNA testing kit can reliably predict whether you’re a genius or not, even if they claim to. And even if the field advances, DNA tests can’t factor in environmental influences on intelligence.
Your genetic makeup determines whether you think your urine smells strange after eating asparagus.
Do you cringe at the smell of your urine after eating asparagus? If so, you're part of the nearly 40 percent of individuals who can detect the scent of asparagus metabolites in urine. This was revealed by a study of almost 7,000 European-American participants, published in the 2016 Christmas issue of The BMJ. (By the way, The BMJ has a tradition of releasing quirky, lighthearted studies around the holiday season, and this asparagus pee research is no exception.) However, there isn’t a single gene to blame for this phenomenon. Instead, multiple olfactory receptor genes—and 871 genetic variations of these genes—play a role in whether you're sensitive enough to detect the asparagus odor.
