Before we get carried away talking about transcription, we'd better step back a little bit and refresh what we know about DNA. We here at Shmoop have told you a lot about DNA, and about how DNA (and the genes it includes) are what makes you you, and your dog, well…a dog. We think it is amazing that if you look at the DNA of a dog (or a mouse, or a monkey, and so on) and compare it to a human's, the DNA will be more the same than different. Gnarly stuff.
Both human and dog DNA are made of the same building blocks: nucleotides. They use the same universal base-pairing laws: adenine pairs to thymine, and cytosine pairs to guanine. The DNA is in a double helix structure. It's replicated by DNA polymerase in a semi-conservative manner, which means that one DNA strand will be used as a template to make a new strand.
DNA is just the beginning though. The diversity we see between organisms, and even between cell types is a result of how our genes are expressed. You can think of DNA as the cell's alphabet. The "DNA letters" can be used to create vastly different biological outputs similar to the way that the English alphabet can be used to create two books on vastly different subject matters. The information in DNA is only selectively expressed, even if the sequence of nucleic acids is the same.
Did you forget about genes already? Here's a little refresh. A gene is a contiguous strand of DNA that is used to create a functional RNA or protein. In other words, a gene is like a word that is made of nucleotide (DNA) letters.
A gene contains both the information that appears in the RNA, and the region of DNA that helps regulate its expression. The information in the RNA generated can then be used to generate a protein.
To make a protein encoded by DNA, the cell uses two steps. The first step, called transcription, is when the cell makes an RNA copy of the information. In the second step, translation, the message in the RNA is translated into a protein, in an entirely new language using amino acids. We'll talk about transcription now, and translation in the next section. Oh, and in case we started boring you with all these details, we'd probably mention that these two steps are kinda important—so important in fact that they define the central dogma of biology.
Don't worry though, it is fairly straightforward. The central dogma is:
DNA → RNA → Protein
Tada. You've now mastered the major take home message from this whole module. But, don't worry, we've got a whole lot more thrilling information to entertain you with.
Transcription makes an RNA copy of the DNA message. Since RNA and DNA are both made of nucleotides, we like to compare transcription to copying your BFF's math homework. The copy won't be exactly identical because it'll be in your handwriting, but the content will be mostly the same. In fact, so similar that it is called plagiarism…something we here at Shmoop definitely don't endorse.
Transcription is also an excellent example of how some basic principles in biology are seen over and over again. Transcription copies some of the basic principles of DNA replication. Therefore, once you have a good grasp of DNA replication, transcription is a cinch. Don't believe us? Let's start by going through the similarities.