We prepared a postcard to explain how many information is stored in the genome of a single cell or in a single human body. To give sense to that large amount of data we calculated the quantity of DIN-A4 papers that would be needed in order to write all the DNA sequence of the genome of a single cell in a standard font (Courier New, 12) and standard margins. This way, everyone without biology or computation* knowledge could also imagine the quantity of information.

*(sometimes the quantity of DNA information is expressed in bytes, which is not suitable for the general population, especially older people). It turns out that a normal somatic human female cell has 2 dotations of 23 chromosomes (including 2 X sex chromosomes) and mitochondrial DNA. This is a total of two times 3,088,286,401 base pairs, according to the latest human genome sequence release (GRCh38.p12). A single DINA-4 page full of characters in Courier New, 12 and standard margins could contain 2773 base pairs written on it. Therefore, to write all the information stored in the base pairs of the genome of a single human cell it would be needed to print 2,186,117 pages on one face. If these pages are then piled up to form a tower (considering the height of a single paper is 0.1mm), it would be 218.61 meters tall (717.2 ft)! Just between the Agbar Tower (the taller building in our city, Barcelona; 142m) and the Eiffel Tower (324m). Scientists have estimated that the human body contains nearly 37.2 trillions of human cells (note that this does not include the microbiota). So...to write all the information condensed in the DNA of one human body it would take a large amount of DINA-4 papers. This amount is so huge that if the papers were arranged in a straight line, the light would spend 2553 years traveling from one end to the other. This is 2553 light-years long! Keep in mind that the distance from the sun to the earth is just 8.3 light-minutes, so imagine the amount of data stored in such a low volume like your body.

Using these examples, the general population can easily understand the information storage capability of DNA. Nearly everyone (including ourselves) was pretty amazed to realize how much information human bodies contain stored in DNA. After this examples, we explained that our sensor was based on a piece of information stored in two genes of the DNA. So this comparisons helped the general population to understand that DNA contains much useful information, which is different between us and that we can extract this information to create a personalized product. This helped us to explain the DNA extraction and PCR process of our project to the general population. This way, they are much better informed about the project and can have an opinion about it. Then, we integrated that informed opinion from the general population in the design of our project. Dedicating effort in explaining the projects in a simple but rigorous way can help teams to receive feedback from the target population. This feedback can be incorporated into the design of the project and hence make it more suitable for the real world.

Synthetic biologists engineer nature to create solutions to real-world problems. We decided to incorporate some synthetic biology into our DNA information storage workshop to expand the general population knowledge about that field. If DNA is able to compact such a large amount of data in a very small volume, why not use it as an information storage system? - would a synthetic biology scientist think. Furthermore, digital information is being generated at an increasing rate and the storage of this information requires a huge amount of servers which take up a lot of space. So why not using DNA to store digital data?

A single DNA base contains more information than one bit. DNA is made from a combination of four different nucleotide residues (A,T,C,G), while one bit can only take up to two values (0 or 1 in binary code). So one DNA base pair could contain two binary code bits of information (i.e. A=00, T=01, C=10, G=11). Therefore, theoretically, information is much more condensed in DNA than in bits.

Actually, there are still several factors making DNA information storage not as practical as current systems. However, the increase in efficiency and the drop in the cost of DNA synthesis and sequencing has dramatically increased the likelihood of using DNA as an information storage system. For this reason, Church et al, 2012 encoded multiple copies of the book he wrote, Regenesis, in DNA and then used next-generation sequencing to read it. Instead of using the maximum compaction system that DNA offers (2 bits per base), the authors used one bit per base (A or C for 0, G or T for 1). This has multiple advantages, one of it being avoiding extreme GC content.

To integrate synthetic biology in our DNA storage workshop we reproduced the work done by Church et al, 2012 to write our own DNA messages. While the authors considered secondary structure, designed a block system to order their data from DNA and encoded words, images, and a javascript file, our system only considered GC content to write messages of a few words or mp3 files in binary code. However, our system was perfectly usable for our purpose. We created a bash script which takes a text input message and converts it to binary by the ASCII code using the xxd command. Then, using a random function, the program assigns a DNA nucleotide to each binary value (A or C to 0, G or T to 1). Finally, it checks if the GC content is between the specified boundaries (by default, 40-60%). Thanks to the random function, the GC content is usually between 50%. Only when encoding single ASCII characters the program needs to perform more than one iteration to get the appropriate GC content. The generated output consists of the written message in the input format, in binary and in DNA. It also incorporates a title recreating the FASTA format used to identify the DNA sequences (and in this case, the message). The program was also adapted to convert songs in mp3 format to DNA sequences, to convert multiple text messages in the same file and to send the generated DNA messages by mail. In addition, the program displayed in a very visual way how the message was being encoded in binary and then in DNA.

We used this program to convert several short text messages about synthetic biology into DNA sequences. We then printed only this DNA sequences with their title and including a guide on how this information is encoded on the other face of the paper. We printed nearly 300 copies of the messages and gave it to students in our university. The message contained information about where to locate the DNA information workshop and an invitation to come in order to decode their DNA message.

This way, we attracted the students to the workshop, where we told them the information about natural information on DNA. In addition, we organized some other small activities related to science and celiac disease (i.e. a guess what contest, in which the participants tried to identify the content of a science picture between two possible options). All the students who came had their message decoded by us. We could quickly identify the message by its title and write down the content of the message in text format in their DNA message paper.

Finally, if the participants correctly identified more than 2 of 3 scientific pictures, we gave them the opportunity to write their own message and have it coded in DNA and sent to their mail by the program we created. Most of the messages consisted of the name of the participants and some student jokes. However, the final objective was to have fun while learning about DNA information storage, so mission accomplished!

Furthermore, it was very satisfactory for us to see the enthusiastic attitude of the students towards that workshop. It seems that most of them find special the fact of having a personal message stored in a DNA sequence which could be then synthesized, introduced to and replicated by a living organism. The program we developed based on the coding system of Church et al, 2012, helped the students to integrate into the topic by engaging on it hands on. Like the examples provided before, this section of the workshop helped translate a difficult concept in a simple but rigorous way to general population. In addition, it served us as a tool to attract people to the workshop and explain them a little bit more about iGEM, synthetic biology and our project.