17 May 2022

Six unbelievable things you probably didn’t know about DNA

By Alison Cranage, Science Writer at the Wellcome Sanger Institute

For the fundamentals of all things DNA, genes and genomes, head to yourgenome.org. Stay with us for the more obscure…

1. A few grams of DNA could store the entire world’s data

And it could be cost-effective pretty soon.

In 2013, researchers at EMBL’s European Bioinformatics Institute (EMBL-EBI) stored, retrieved, and reproduced over five million bits of data using DNA. The data included all 154 of Shakespeare’s sonnets, a photo of EMBL-EBI, an audio clip from Martin Luther King’s famous “I have a dream” speech, Watson and Crick’s classic research paper on DNA structure, and a file describing how the data were converted.

After the files were transformed into DNA code, this was synthesised and stored. To retrieve the information, the team sequenced the DNA, and reconstructed the original files, with 100 per cent accuracy¹.

Theoretically, this DNA-based storage scheme could be scaled up to store the entire world’s information. DNA is durable, remaining stable over thousands of years, and it is very, very compact.

In 2012, it was estimated that the entire world’s information at the time – 1.8 zettabytes – could be stored in about four grams of DNA².

2. There are more than four DNA bases

Ask a scientist about DNA and they’ll probably mention four ‘bases’: A, T, C and G, which make up its chemical structure. But there are more.

Little-known base J, or ‘β-D-Glucopyranosyloxymethyluracil’ to give its full, unpronounceable name, is found in some parasites’ DNA, including trypanosomes and Leishmania³.

Plus there are synthetic bases (P, Z, B and S), which have been made into Hachimoji (eight letter) DNA⁴.

You will be able to impress any biologist you meet with this one. You’re welcome.

3. Your DNA is 50 per cent the same as a cabbage

It is thought that every single living thing on Earth (apart from viruses) evolved from the last universal cellular ancestor (LUCA), about 4 billion years ago⁵.

It’s likely that the LUCA was a small, single-celled organism, with a ring-shaped coil of DNA. The LUCA evolved into all of the cellular life forms we see today.

Single-celled bacteria and 37 trillion-celled humans both have DNA, which contains the instructions to build their cell, or cells. So, there are similarities. The more closely related the organisms, the more similar their DNA is.

In the case of cabbage versus human, our DNA is 50 per cent the same.

We all have our origins in the same primordial soup.

Woman holding fresh cabbage on color background

4. You can get animal DNA out of thin air

Earlier this year, two teams of scientists vacuumed up some air from zoos in the UK and Denmark, and sequenced the DNA in it⁶. They found fragments of DNA from species living in the zoo – including birds and mammals, DNA from local wildlife, as well as DNA from species used as zoo animal food, such as fish. In some cases, the animals they found were hundreds of meters away from where they sampled the air.

Studies of so-called environmental DNA, or eDNA, have really taken off over the last ten years, thanks to technological advances in sequencing. Researchers have been able to study DNA samples from surfaces, soils or water, and this was the first proof that you can take DNA from the air, too.

Wherever it comes from, it is hoped that environmental DNA can be used to help monitor biodiversity and endangered species.

5. Most of your genes aren’t human

It is estimated that there are about the same number of bacterial cells as human cells in our bodies – around 37 trillion.

The communities of microbes that inhabit our gut, skin and other mucosal surfaces are collectively known as the microbiome, and they are essential for our bodies to function. They help digest our food, prevent infection and interact with our immune system. We wouldn’t survive without them.

Our microbiome is so important that we have evolved to produce sugars in breast milk that are indigestible to humans, but promote growth of beneficial bacteria in a newborn’s gut⁷.

Humans can be described as ‘holobionts’ – the human host plus communities of hundreds of different species of bacteria, viruses and fungi, all living together. Bacteria are smaller than human cells and while individually their genomes are more than a thousand times smaller than the human genome, collectively they contain 150 times more genes.

6. Even your human DNA isn’t all human

Not counting the bacteria, viruses, fungi and other species that live in and on us, there are remnants of other species within a human genome itself.

These are known as mobile genetic elements or selfish genetic elements. There are several different types, including ‘jumping genes’.

Some of these DNA sequences are thought to have originated from viruses, and they integrated themselves into the human genome. The sequences have the ability to make more copies of themselves, which then also get inserted into the genome, resulting in large, repetitive areas of DNA. They appear to be out for themselves, replicating to survive – hence the term ‘selfish’⁸.

50 per cent of the human genome is thought to be made up of mobile genetic elements.

Barbara McClintock was awarded the 1983 Nobel Prize for her discovery of mobile genetic elements.