You are a miracle. Not in the sense of “it’s a miracle you got this far” (though this applies to some of us) but you are a scientific miracle. Inside each of your cells, one of the smallest parts that make up “you”, is an extraordinary amount of information. Information we have barely begun to scratch the surface of understanding. Not only does each cell contain a small community of builders, energy makers, decision makers etc. but this community talks to other communities across vast distances to create organs, muscle, bone and in essence create you.
But how do these cells know who they are and what to do? How does a brain cell know it’s a brain cell and not a skin cell or a liver cell? How do they know their function in creating and maintaining you? This is down to your genes and the study of your genes is called genetics.
Your cells are communities and have all the “buildings” you would have in a town (power supply, manufacturers etc.). The most important building in your cell is the library. The library contains all of the knowledge about you and your ancestors for millions of years. Like with any book editions change, books get updated and books get lost but the information is still there for you to access.
As you know libraries contain books. Some books are very important and are read daily (for example the dictionary) while some books are only read when needed (for example a book on first aid) and lastly we have the books that hold very little useful information (for example trashy novels you read on holiday). The books are your genetic code and there is a lot of it. In fact if you took all the genetic information in an individual cell and laid it out like string it would measure 1 meter.
A gene is a book that creates an action. When you read a book you form an opinion on it and that opinion creates an idea, which you can act upon or share. When a gene is “read” this leads to the creation of an “idea” or RNA. You can act upon this “idea”, which leads to an “action” or makes a Protein. Proteins are used for everything in a cell, from builders, communication and regulation of the cells internal environment (temperature, amount of water, pressure etc.).
For example you want to build a table so you read a book (gene) about carpentry. From that book you develop an idea (RNA) of how you want to build your table and copy it out in your own words. You then build your table (protein). That table can now be used however you want. This process is called transcription (genes to RNA) and translation (RNA to Protein).
The books that are read daily are called “housekeeping” genes. These keep your cells working on the most basic levels (food, water, energy). The useful genes are called “coding genes”. This means that “reading” these will create RNA and protein(s). You have about 20,000 “coding genes” in your library. The final part of your genetic code is “junk DNA”. These are the books that cannot create RNA or protein(s).
The books in every single cell in your body are identical. But your cells don’t all act the same. This is because certain cells only allow access to certain books. Imagine your library is divided into sections. For simplicity, the sections are your organs (e.g. brain, liver, skin) as well your blood and your immune system. If a cell is a brain cell it will only have access to the books in the brain cell section. The other sections are closed off. The only cells that have complete access to your entire library are “stem cells”. Stem cells are cells that can become any cell it wants. They are the roots of the tree from which all other cells come from. Once a cell becomes specialized (e.g. brain, liver or skin) it cannot be any other cell.
Genes, like books, are made up of a series of letters. There are four letters in your genetic code: A (Adenosine), T (Thymine), G (Guanine) and C (Cytosine). Thousands of these letters are organized into specific patterns (e.g. AAAGCGTTCGAACG – this is not a real gene). The pattern is read like a book and converted into a specific RNA and protein. Interestingly, these books can be read forwards and backwards. They can also be cut up into sections (like a trilogy). Each different way of reading the book creates a different “idea” and “action”. However, there is always a beginning, middle and end.
But who reads these books? The readers are called "transcription factors". They go into the libraries catalog and are sent to the book(s) they want. They transcribe the gene into RNA and pass it over to "workers" called "ribosomes" which convert the RNA code into protein. Neat!
Different books are also read together. For example reading a French book with a French dictionary. One requires the other. While single books are read for simple ideas (for example eye colour or hair colour), multiple books are read for complex ideas (for example height).
While you are created from your genes, your genes don’t determine everything about you. It’s important to keep in mind that your environment has a vital role to play in forming you. What you eat and drink, what pollutants you’re exposed to as well as what pathogens you’re exposed to all have an impact on you.
You are a miracle.
This is a basic introduction into genetics. As you can imagine this is a massive, complex area of study. If you have any questions or if you want more detail please don't hesitate to contact me!
My name is Caitriona and I am a PhD student at Imperial College London, UK.