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Explainer: The Basics of DNA and Genetic Systems

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Explainer of DNA and Genetic Systems

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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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.

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Healthcare

Visualized: What Lives in Your Gut Microbiome?

The human gut microbiome contains a world of microbes. We look at the the bacteria that deeply affect our health and well-being.

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Visualized: What Lives in Your Gut Microbiome

Inside all of us lies a complex ecosystem of microbes. It includes bacteria, fungi, and even viruses that live in virtually every part of our bodies.

Researchers are continuing to discover how deeply connected our overall gastrointestinal health—gut health—is to these microbes.

Because bacteria outnumber all other microbes, we take a look at which ones live inside of us and what they do.

The Bacteria of the Gut Microbiome

The gut microbiome is composed of six main types of microbes. Each of these types of microbes has a unique function and role within the human body:

  • Firmicutes: Firmicutes break down complex carbohydrates and produce short-chain fatty acids for energy. They help maintain the functioning of the gut barrier, which obstructs bacteria, harmful microorganisms, and toxins from entering the bloodstream through the intestinal tracks. Firmicutes are also linked to obesity and metabolic disorders when imbalanced.
  • Actinomycetota: Actinomycetota break down complex carbs and produce vitamins B12 and K2, which are crucial for calcium absorption and energy generation in the body. They also protect the gut from harmful pathogens.
  • Pseudomonadota: Pseudomonadota lowers the gut’s redox potential, a measure of the balance between oxidants and antioxidants in the gastrointestinal tract. This is important for breaking down, storing, and using energy. They do this by producing short-chain fatty acids and breaking down complex molecules, promoting the growth of other beneficial gut microbes.
  • Fusobacteriota: Fusobacteriota can activate inflammatory responses to fight pathogens. But when imbalanced, they can contribute to inflammation and disease, such as periodontal disease.
  • Bacteroides: Bacteroides break down complex carbohydrates, regulate the immune system, and produce vitamins and metabolites important for overall health in the human gut microbiome.
  • Other: The “other” category includes a diverse range of microbes that contribute to various functions within the gut. These include various types of bacteria including TM7 (oral bacteria), cyanobacteria, acidobacteria, and verrucomicrobiota.

Dynamic Composition of the Microbiome

Interestingly, the proportions of these six microbe populations vary throughout the gastrointestinal tract.

Section of Gut MicrobiomeExponential Microbial Population (CFU/ml)Dominant Microbe
Mouth10⁵Firmicutes
Esophagus10⁷Firmicutes
Stomach10³Actinomycetota
Duodenum (Small Intestine)10³Firmicutes
Jejunum (Small Intestine)10⁵Firmicutes
Ileum (Small Intestine)10⁸Firmicutes
Large Intestine10¹⁰-10¹²Bacteroides

The presence, absence, and dominance of each of these microbes is based on their functionality. For example, in the mouth and esophagus, the microbial populations are relatively low. But the dominant microbe found here, Firmicutes, helps begin the process of breaking down sugars and carbohydrates from ingested food.

Meanwhile, the stomach is a harsh environment, with low pH levels that limit microbial growth. A small population of microbes is still present here.

The microbial population becomes more diverse in the small intestine. Here, Firmicutes and Actinomycetota are the dominant species, but Bacteroides and other microbes begin to make up a more substantial portion of the population.

The microbial population further diversifies in the large intestine, with Bacteroides and other microbes making up the majority of the population.

These proportions of bacteria in the gut microbiome represent the typical ratios for the average human body. But they can be influenced by factors including medical history, diet, age, and even geographical location.

The Gut-Brain Axis

The six microbe populations have effects way outside the gastrointestinal tract too.

The Gut-Brain Axis is a two-way link between the gut and the brain. This connection involves physical pathways and various forms of communication, including hormones, metabolism, and immunity.

Through these connections, the gut sends the brain signals when troubled. A distressed stomach or intestine is linked to anxiety, stress, depression, and other mental health issues. Irritable bowel syndrome (IBS) is another example of a disease influenced by the gut microbiome.

At the same time, the brain also signals the gut when distressed. Scientists believe that emotions like anger, anxiety, sadness, and happiness trigger gut issues.

Towards a Healthy Gut

The gut is known as our body’s “second brain” and more and more people are now paying close attention to their gut health.

Over the last two decades, we’ve gained a better understanding of how the microbiome affects human health. One example of this is the gut-brain axis. Changes in the microbiome have also been connected to various diseases.

Understanding this microbiome has opened up new opportunities in medicine and healthcare, as the knowledge of the role of every microbe could also uncover new treatments for illnesses linked to it.

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