In this video, we're going to briefly discuss how DNA replication produces replicated chromosomes. Later in our course, we will talk in more detail about the process of DNA replication. But in this video, we're only going to lightly introduce DNA replication just enough to help you understand how it produces replicated chromosomes. First, we need to recall from some of our previous lesson videos that before a cell can divide, it's critical that the DNA must be replicated.
The term 'replicated' has a few synonyms that can be commonly used by your professors or in your textbook. The term replicated is synonymous with 'synthesized' and 'duplicated'. Thus, DNA replication, DNA synthesis, and DNA duplication all mean the same thing. We can say that this process of DNA replication is a process that produces an exact copy of all the DNA inside of a cell. This is critical for a cell to do before it divides because when a single cell divides into two separate cells, each of those cells needs a copy of the DNA, and that can only happen if DNA replication occurs first.
This process of DNA replication will convert unreplicated chromosomes, or chromosomes that have not yet been replicated, into replicated chromosomes, or chromosomes that have gone through DNA replication. These replicated chromosomes that have gone through DNA replication are going to have two identical sister chromatids. The term 'sister' is used to imply that these chromatids are identical to one another in terms of their DNA sequence. The term 'chromatid' can be defined as half of a replicated chromosome, and the chromatids are going to be joined to one another at a region called the centromere, which can be thought of as the waist position of the chromosome.
If we look at our image, notice on the left-hand side what we're showing you is a single unreplicated chromosome, which kind of looks like a straight line in this image. We can also think of a single unreplicated chromosome as just one chromatid. After DNA replication, notice on the right-hand side what we have is a single replicated chromosome. This replicated chromosome has gone through the process of DNA replication, and what you'll notice is that our unreplicated chromosome is highlighted, and with this replicated chromosome, we still have that same unreplicated chromosome present. However, you'll notice that the unreplicated chromosome has been replicated. So here, what we have is another identical copy of the pink highlighted region.
We call these regions chromatids, and these two can be said to be two identical chromatids, or in other words, they are sister chromatids. What you'll notice is that this sister chromatid and this sister chromatid are attached to each other at this one position right here that we call the centromere. This is critical information because we can tell if a chromosome has gone through DNA replication because if the chromosome somewhat looks like an X, as you see here, then we know that it's gone through DNA replication. But if the chromosome does not look like an X and looks more like a straight line, then we can say that it is an unreplicated chromosome that has not yet gone through DNA replication.
This can be very helpful information to note as we move forward and talk more about cell division. But for now, this here concludes our brief lesson on how DNA replication produces these replicated chromosomes, and we'll be able to get some practice as we move forward. So, I'll see you all in our next video.