Equalitarian Blood

Blood flows around the body all the time, yet we barely see it unless we suffer from an accident. If this were the case, and we lost too much of it, we’d need a blood transfusion. But it is not as easy as just putting blood from one individual into another: you need to test it and make sure the blood is compatible.


Can you guess what antigens these red blood cells have?

This occurs because human blood can be divided into many categories. The most common one is the ABO group classification, which divides blood into four types: A, B, AB and O. In each, red blood cells (those cells specialised in carrying oxygen around the body) have a specific antigen depending on the blood type. For example, if you have group A blood, you will have A antigens; if you have AB blood, you will have A and B antigens; and most importantly, if you have O blood, you will have no antigens.

Each antigen stimulates a response from our immune system to produces antibodies against the other antigens. So if you have blood group A, you will produce antibodies that will destroy cells with antigen B, and vice versa. This is potentially very dangerous, because if you give someone of type A blood from a person of type B, the antibodies can attack each other’s red blood cells and wreck havoc in our bodies.

When it comes to transfusing blood, the best one is group O- since it has no antigens, so there is no way your body can attack it. That is why we call it universal, since it works for anyone, no matter their blood type. This makes it very sought after for blood transfusions, but there isn’t always plenty of it available.

But what if we could convert all blood into O type blood? We can’t change the genotype of adults so that their body produced it, but we can change the blood itself after the blood has been donated. The most successful way to do this would be to insert bacterial enzymes into the blood which can recognise antigens in the red blood cells and cut them off so they are just like red blood cells from O group blood.

In the experiment which created this mechanism, the original enzyme worked mostly with cells from group B only, so to make it effective on cells from group A too they used a very interesting method called directed evolution. It’s just as it sounds: they grew the bacteria that produce this type of enzyme, and slowly mutated their genome (by adding bases to their DNA) so that every generation produced a better enzyme. At the end of the experiment, after 5 generations of bacteria, the final enzyme was produced, which not only could severe A antigens, but was also an impressive 170 times more efficient than the original one.

Yet this method is still not perfect: the enzyme can’t modify all the thousands of red blood cells in a sample of blood and therefore can’t make it completely safe, as there will still be some red blood cells with antigens present. But with enough time, the scientists hope to perfect it and make the technique available so blood transfusions are easier to carry out.

XNA Alternative

DNA and RNA have always been considered miracle molecules thanks to their ability to self-replicate and create life. Everyone thought that they were the only molecules that could carry information on how to code for an organism and pass this down for generations. But what if I told you there were other molecules capable of doing the same thing?

This group of molecules is called XNAs (Xeno Nucleic Acids) and they all are a polynucleotide strands but each with a different repeating monomer. They still have a base and a phosphate group attached; what changes is the sugar in them. Whilst DNA uses deoxyribose and RNA uses ribose, XNA can use a wide variety of sugars, like theorose, or other unrelated chemicals, like peptides.


This is a normal DNA strand – XNA is the same but with a different sugar in the nucleotide

Not only do they copy the structure of a nucleotide and therefore form a nucleic acid, but they can also store information in the form of bases. However, to make XNA carry bases in a desired order, scientists have to use an enzyme that copies the coding from a DNA strand and passes it onto an XNA strand. Once there, another enzyme can read the bases in the XNA and copy them onto DNA, and if needed, back to XNA. This means that an old XNA can technically pass information to a new XNA molecule, even if it uses an intermediate molecule; this process is basically evolution.

But this discovery is from back 2012. The current news involves XNA being able to act as enzymes, apart from encoding possible genetic information. They still can’t form copies of themselves in the traditional sense, but they can manipulate RNA and even add XNA fragments to an XNA strand. The fact these molecules are enzymes and can modify themselves to some extent makes it more feasible that at some point they will be able to self-replicate, and behave just like DNA did, to evolve into a new type of life.

It is also further proof showing that XNA is a viable alternative to both DNA and RNA, and that the reality that all living organisms we know use these nucleic acids could be arbitrary. In fact, it could be perfectly possible than in other galaxies, organisms use XNAs instead of DNA. Of course, this is only a theory, and we have to take into account the conditions of an environment without any life. RNA and DNA could have developed because they were more likely to appear in the first place, for a reason unbeknownst to us yet.