Visualizing the Relationship Between Cancer and Lifespan
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Visualizing the Relationship Between Cancer and Lifespan

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Visualizing the Relationship Between Cancer and Lifespan

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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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Science

Explainer: The Basics of DNA and Genetic Systems

All living things have a genetic system made up of DNA. This graphic explores the basics of DNA composition and structure.

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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).

While most living things rely on a mix of DNA and RNA for cellular reproduction, some viruses just use RNA to store their genetic information and replicate faster.

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:

OrganismKingdomSize of genomes (number of base pairs)
Poplar treePlant500,000,000
HumanAnimal3,200,000,000
ChimpanzeeAnimal3,300,000,000
Marbled lungfishAnimal130,000,000,000
DogAnimal2,400,000,000
WheatPlant16,800,000,000
PufferfishAnimal400,000,000
Canopy plantPlant150,000,000,000
Mouse-ear cressPlant140,000,000
CornPlant2,300,000,000
MouseAnimal2,800,000,000
MossPlant510,000,000
Fruit FlyAnimal140,000,000
C. ruddiiBacteria160,000
S. pombeFungi13,000,000
S. cerevisiaeFungi12,000,000
S. cellulosumBacteria13,000,000
H. pyloriBacteria1,700,000
E. coliBacteria4,600,000
Panadoravirus s.Virus2,800,000
HIV-1Virus9,700
Influenza AVirus14,000
BacteriophageVirus49,000
Hepatitis D virusVirus1,700

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.

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Explainer: The Different Types of Volcanoes on Earth

This graphic provides a brief introduction to volcanoes, explaining their different types of shapes and sizes, and how they erupt.

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Infographic explaining how volcanoes are formed and different types

Explainer: The Different Types of Volcanoes on Earth

Even if you don’t live near a volcano, you’ve been impacted by their activity.

It’s estimated that more than 80% of our planet’s surface has been shaped by volcanic activity. They’ve helped create our mountain ranges, plains, and plateaus, and have even helped fertilize the land that we now use to grow crops.

These critical mounds come in many shapes and sizes. This graphic by Giulia De Amicis provides a brief introduction to volcanoes, explaining their different types of shapes and eruptions.

Types of Eruptions

A volcano starts to form when molten rock rises from a crack in the Earth’s surface, which often emerge along tectonic plate boundaries.

Magma rises to the Earth’s surface because it’s lighter than rock. When it surfaces or erupts, it’s referred to as lava.

There are various types of volcanic eruptions, depending on the lava’s temperature, thickness, and composition. Generally speaking, high gas content and high ​​viscosity lead to explosive eruptions, while low viscosity and gas content lead to an effusive, or steadily flowing, eruption.

The Four Main Types of Volcanoes

Volcanoes vary in size and structure, depending on how they’re formed. Most volcanoes types fall into four main groups:

Shield Volcanoes

Shield volcanoes are built slowly, from low-viscosity lava that spreads far and quick. The lava eventually dries to form a thin, wide sheet, and after repeated eruptions, a mount starts to form.

From the top, these types of volcanoes look like a shield, hence the name. While these volcanoes take a while to form, they aren’t necessarily low. In fact, the world’s tallest active volcano, Mauna Kea in Hawaii, is a shield volcano.

Stratovolcanoes

Also known as composite volcanoes, stratovolcanoes are built relatively fast, at least compared to shield volcanoes. This is because, in between lava eruptions, composite volcanoes emit ash and rock, which helps add structure to the mound rather quickly.

Some well-known composite volcanoes are Mount Fuji in Japan, Mount St. Helens in Washington, and Mount Cotopaxi in Ecuador.

Volcanic Domes

Opposite to shield volcanoes, volcanic domes are formed when lava is highly-viscous. Because the thick lava can’t travel very far, it starts to pool around the volcano’s vent.

This can sometimes create a pressure build-up, meaning dome volcanoes are prone to explosive eruptions.

Cinder Cones

These types of volcanoes typically don’t release lava. Rather, their eruptions typically emit volcanic ash and rocks, known as pyroclastic products.

Cinder cones are characterized by a bowl-shaped crater at the top, and usually don’t exceed 400 m (1,312 ft) in height.

How Volcanoes Benefit the Earth

Volcanoes have a number of ecological benefits. Once broken down, volcanic materials create exceptionally fertile soil, which can help build prospering new habitats for animals and plants.

Volcanic eruptions can also help cool our climate. When a volcano explodes, ash and sulfur gas from the eruption combine with water droplets and get trapped in the atmosphere for years. This has a cooling effect which is extremely beneficial to us, especially given our current global warming situation.

Dr. Tracy Gregg, associate professor for the University at Buffalo’s geology department, told Accuweather that “volcanoes have actually helped to keep the world about 2 to 3 degrees cooler than it otherwise may be.”

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