Explainer: The Basics of DNA and Genetic Systems
While there is great diversity among living things, we all have one thing in common—we all rely on a genetic system made up of DNA and/or RNA.
But how do genetic systems work, and to what extent do they vary across species?
This graphic by Anne-Lise Paris explores the basics of DNA and genetic systems, including how they’re structured, and how they differ across species.
Composition of Genetic Systems: DNA and RNA
A genetic system is essentially a set of instructions that dictate our genetic makeup—what we look like and how we interact with our environment.
This set of instructions is stored in nucleic acids, the two main types being deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA is made up of four molecules, known as nucleotides: Adenine (A), Thymine (T), Cytosine ( C), and Guanine (G). These nucleotides are grouped in sets of two, which are called base pairs.
Size of Genomes Across Different Organisms
Human DNA is made up of approximately 3.2 billion base pairs that are tightly wound up and stored in our cells. If you were to unwind and measure the DNA stored in a single human cell, it would be about 2 meters (6.5 feet) long!
This lengthy DNA is stored in pairs of chromosomes. A full collection of chromosomes, or an entire set of genetic information, is referred to as a genome.
Genomes vary in size, depending on the organism. Here is a look at 24 different species and the size of their genomes, from animals and plants to bacteria and viruses:
|Organism||Kingdom||Size of genomes (number of base pairs)|
|Hepatitis D virus||Virus||1,700|
The Marbled Lungfish has the largest known animal genome. Its genome is made up of 130 billion base pairs, which is about 126.8 billion more than the average human genome.
Comparatively, small viruses and bacteria have fewer base pairs. The Hepatitis D virus has only 1,700 base pairs, while E. coli bacteria has 4.6 million. Interestingly, research has not found a link between the size of a species’ genome and the organism’s size or complexity.
In fact, there are still a ton of unanswered questions in the field of genome research. Why do some species have small genomes? Why do some have a ton of redundant DNA? These are still questions being investigated by scientists today.
This article was published as a part of Visual Capitalist's Creator Program, which features data-driven visuals from some of our favorite Creators around the world.
All the Contents of the Universe, in One Graphic
We explore the ultimate frontier: the composition of the entire known universe, some of which are still being investigated today.
All the Contents of the Universe, in One Graphic
Scientists agree that the universe consists of three distinct parts: everyday visible (or measurable) matter, and two theoretical components called dark matter and dark energy.
These last two are theoretical because they have yet to be directly measured—but even without a full understanding of these mysterious pieces to the puzzle, scientists can infer that the universe’s composition can be broken down as follows:
|Free hydrogen and helium||4%|
Let’s look at each component in more detail.
Dark energy is the theoretical substance that counteracts gravity and causes the rapid expansion of the universe. It is the largest part of the universe’s composition, permeating every corner of the cosmos and dictating how it behaves and how it will eventually end.
Dark matter, on the other hand, has a restrictive force that works closely alongside gravity. It is a sort of “cosmic cement” responsible for holding the universe together. Despite avoiding direct measurement and remaining a mystery, scientists believe it makes up the second largest component of the universe.
Free Hydrogen and Helium
Free hydrogen and helium are elements that are free-floating in space. Despite being the lightest and most abundant elements in the universe, they make up roughly 4% of its total composition.
Stars, Neutrinos, and Heavy Elements
All other hydrogen and helium particles that are not free-floating in space exist in stars.
Stars are one of the most populous things we can see when we look up at the night sky, but they make up less than one percent—roughly 0.5%—of the cosmos.
Neutrinos are subatomic particles that are similar to electrons, but they are nearly weightless and carry no electrical charge. Although they erupt out of every nuclear reaction, they account for roughly 0.3% of the universe.
Heavy elements are all other elements aside from hydrogen and helium.
Elements form in a process called nucleosynthesis, which takes places within stars throughout their lifetimes and during their explosive deaths. Almost everything we see in our material universe is made up of these heavy elements, yet they make up the smallest portion of the universe: a measly 0.03%.
How Do We Measure the Universe?
In 2009, the European Space Agency (ESA) launched a space observatory called Planck to study the properties of the universe as a whole.
Its main task was to measure the afterglow of the explosive Big Bang that originated the universe 13.8 billion years ago. This afterglow is a special type of radiation called cosmic microwave background radiation (CMBR).
Temperature can tell scientists much about what exists in outer space. When investigating the “microwave sky”, researchers look for fluctuations (called anisotropy) in the temperature of CMBR. Instruments like Planck help reveal the extent of irregularities in CMBR’s temperature, and inform us of different components that make up the universe.
You can see below how the clarity of CMBR changes over time with multiple space missions and more sophisticated instrumentation.
What Else is Out There?
Scientists are still working to understand the properties that make up dark energy and dark matter.
NASA is currently planning a 2027 launch of the Nancy Grace Roman Space Telescope, an infrared telescope that will hopefully help us in measuring the effects of dark energy and dark matter for the first time.
As for what’s beyond the universe? Scientists aren’t sure.
There are hypotheses that there may be a larger “super universe” that contains us, or we may be a part of one “island” universe set apart from other island multiverses. Unfortunately we aren’t able to measure anything that far yet. Unravelling the mysteries of the deep cosmos, at least for now, remains a local endeavor.
Visualizing the Relationship Between Cancer and Lifespan
New research links mutation rates and lifespan. We visualize the data supporting this new framework for understanding cancer.
A Newfound Link Between Cancer and Aging?
A new study in 2022 reveals a thought-provoking relationship between how long animals live and how quickly their genetic codes mutate.
Cancer is a product of time and mutations, and so researchers investigated its onset and impact within 16 unique mammals. A new perspective on DNA mutation broadens our understanding of aging and cancer development—and how we might be able to control it.
Mutations, Aging, and Cancer: A Primer
Cancer is the uncontrolled growth of cells. It is not a pathogen that infects the body, but a normal body process gone wrong.
Cells divide and multiply in our bodies all the time. Sometimes, during DNA replication, tiny mistakes (called mutations) appear randomly within the genetic code. Our bodies have mechanisms to correct these errors, and for much of our youth we remain strong and healthy as a result of these corrective measures.
However, these protections weaken as we age. Developing cancer becomes more likely as mutations slip past our defenses and continue to multiply. The longer we live, the more mutations we carry, and the likelihood of them manifesting into cancer increases.
A Biological Conundrum
Since mutations can occur randomly, biologists expect larger lifeforms (those with more cells) to have greater chances of developing cancer than smaller lifeforms.
Strangely, no association exists.
It is one of biology’s biggest mysteries as to why massive creatures like whales or elephants rarely seem to experience cancer. This is called Peto’s Paradox. Even stranger: some smaller creatures, like the naked mole rat, are completely resistant to cancer.
This phenomenon motivates researchers to look into the genetics of naked mole rats and whales. And while we’ve discovered that special genetic bonuses (like extra tumor-suppressing genes) benefit these creatures, a pattern for cancer rates across all other species is still poorly understood.
Cancer May Be Closely Associated with Lifespan
Researchers at the Wellcome Sanger Institute report the first study to look at how mutation rates compare with animal lifespans.
Mutation rates are simply the speed at which species beget mutations. Mammals with shorter lifespans have average mutation rates that are very fast. A mouse undergoes nearly 800 mutations in each of its four short years on Earth. Mammals with longer lifespans have average mutation rates that are much slower. In humans (average lifespan of roughly 84 years), it comes to fewer than 50 mutations per year.
The study also compares the number of mutations at time of death with other traits, like body mass and lifespan. For example, a giraffe has roughly 40,000 times more cells than a mouse. Or a human lives 90 times longer than a mouse. What surprised researchers was that the number of mutations at time of death differed only by a factor of three.
Such small differentiation suggests there may be a total number of mutations a species can collect before it dies. Since the mammals reached this number at different speeds, finding ways to control the rate of mutations may help stall cancer development, set back aging, and prolong life.
The Future of Cancer Research
The findings in this study ignite new questions for understanding cancer.
Confirming that mutation rate and lifespan are strongly correlated needs comparison to lifeforms beyond mammals, like fishes, birds, and even plants.
It will also be necessary to understand what factors control mutation rates. The answer to this likely lies within the complexities of DNA. Geneticists and oncologists are continuing to investigate genetic curiosities like tumor-suppressing genes and how they might impact mutation rates.
Aging is likely to be a confluence of many issues, like epigenetic changes or telomere shortening, but if mutations are involved then there may be hopes of slowing genetic damage—or even reversing it.
While just a first step, linking mutation rates to lifespan is a reframing of our understanding of cancer development, and it may open doors to new strategies and therapies for treating cancer or taming the number of health-related concerns that come with aging.
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