What is DNA and How Does it Work?

Imagine that you want to build a robot. You don't know exactly how to do it, but there's a book in the library with instructions. You go to the library and find the book, but there's a problem. The library doesn't allow you to take the book out, and you can't bring the materials to build the robot into the library. So what do you do? You decide to scan and print parts of the book to take back home with you. Now you can build your robot. This process is very similar to how DNA works. Before we get into that, however, what exactly is DNA? Quite simply, DNA is nothing but a giant molecule. The phrase giant molecule might sound like an oxymoron, but it's actually a fitting description, considering that a single DNA strand can be as long as a human being, up to six feet in length. DNA is the molecule's common name, but its proper title is deoxyribonucleic acid. It has a twisting, helical structure, much like a twisted ladder. Now, this giant molecule is made up of even smaller molecules. The sides of the ladder are composed of sugar and phosphate molecules, while the rungs of the ladder are made of four chemical letters, A for adenine, T for thymine, G for guanine, and C for cytosine. These four letters come in pairs that are destined to match with each other. A pairs with T, while C pairs with G. This repeats on and on until we form a giant molecule of DNA. If you think of a cell as a huge city, the DNA is stored in the nucleus, which is like the library found in the head office of the cell. DNA acts like an instruction manual for cells on how to make proteins, which are the cell's very own machines that literally run every aspect of the cell. Proteins are made of tiny blocks called amino acids. There are about 20 different amino acid Lego blocks that are available to our system. They join together in different ways to create all the proteins that compose a cell. DNA can be read like a book, where you read only the letter on one side of the DNA. The DNA is also read in three-letter codes, called codons. Each codon specifies a particular amino acid. Many codons put together make up a gene. DNA has thousands of genes that lay the groundwork for thousands of different proteins. These proteins, with a few changes along the way, go on to make up cells, which in turn form tissues, which subsequently form organs. All the organs, when put together, form a living being. However, when creating these proteins, a cell might run into a little problem. The amino acids are found in the cytoplasm, while the DNA is found in the nucleus. The DNA isn't allowed to leave the nucleus, just as you weren't allowed to remove the robot-building book from the library. The amino acids, similarly, aren't allowed inside the nucleus, just as you weren't allowed to bring your building materials into the library. So, to solve this problem, certain enzymes in the nucleus do exactly what you did. They copy the DNA. This copy is called messenger ribonucleic acid, or mRNA, which the enzymes can smuggle out of the headquarters and into the outer parts of the cell, where the copy can be used in protein workshops, called ribosomes. Ribosomes are the protein-building workshops of the cell. The ribosomes read the information in the DNA, via the mRNA, in order to develop the final protein product. Thus, the ribosome will read one codon, and then add the correct amino acid. This process continues until the instructions end and the protein is made. The resultant living being that is formed is heavily dependent on the sequence and the number of DNA bases. The complete instruction manual for human beings, for example, has three billion letters or bases. This complete DNA instruction manual is known as a genome. Around 99% of the bases in the human genome are the same in all people. It is the remaining 1% that makes each of us unique. Though scientists have uncovered how DNA works, there is still a great deal that we don't know. Building life isn't quite like building a robot. DNA, proteins, and RNA interact with each other in complex ways to form and sustain living things. DNA is also helping scientists investigate the history of life, while genetic engineering might help us modify DNA in the future. Many of these processes are being actively researched by scientists, and their ramifications could change life as we know it. Clearly, this blueprint of life still has plenty of surprises in store for the world of science.