In humans, the nucleus of each of our 37 plus trillion cells contain our DNA, and yes, you heard that right. Almost each and every one of our cells contain the exact same DNA. So essentially, the cells that make up your nose have the same exact DNA as the cells that make up your toes. The information in DNA is stored as a code made up of four chemical basis. First there's adenine, you see as an A, guanine as a G, cytosine C, and thiamine T. Now I want you to follow me into the nucleus of the cell so we can look at this together. So as you can see here, there's a lot going on, but let's focus first on this part over here to the left. As you can see, this is a strand of DNA and you can see the pattern that is always made in DNA where thiamine bonds with adenine, and cytosine bonds with guanine, always. These bonds are known as base pairs and humans have about 150 million of these. Now one of the most important properties of DNA is that it can make a copy of itself for the purpose of creating new cells, this is a process known as replication. The structure of DNA makes that easy because each side of the double helix runs in the opposite direction, so that when it's unzipped, each side can serve as a pattern for the other side. But what you see here isn't replication, it's another process that often gets confused with replication and it's known as transcription. Now during transcription, only a portion of the cell's DNA is unzipped, and instead of making a copy of itself, it creates an RNA molecule. RNA molecules differ from DNA molecules in a couple of key ways. One; they're comprised of a single cell like you see here, and two; they include the nucleotide uracil in place of thiamine. So instead of adenine bonding with thiamine like a DNA, in RNA, adenine bonds with uracil. Now the role of RNA is to make proteins which in turn are the building blocks of all living things. So the way this works is that when the RNA polymerase enzyme attaches itself to the template strand of DNA, it begins assembling a new chain of RNA nucleotides known as messenger RNA or mRNA. As this chain grows, it separates from the template and carries the DNA's message from the nucleus to the ribosomes in the cell's cytoplasm, and it's there that it will build the required proteins. So you might be asking, why is this important? Well, the information stored in our DNA is essential for life, so if and when a cell dies, the body has to be able to replace that cell. The only way to do that is to first make a copy of the information that the cell contained. RNA, well, that's what makes our proteins and proteins play a lot of roles in the body. They do most of the work of the cells and make up the structure and function and regulation of the body's tissues and organs. Why is this important for you to know? This just happens in our bodies without us thinking about it. But you see as much as we may wish it so, this process doesn't always go as planned and mistakes can be made in DNA replication, RNA transcription, and translation. These mistakes, also known as mutations can be simple and may not have any known effect on the body. While others, well, they can be quite severe and lead to serious consequences such as cancer.
