DNA Replication

by Jason Amores Sumpter
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in this video, we're going to briefly discuss how DNA replication produces replicated chromosomes. And so later in our course we're going to talk a lot more details and go way more in depth about this 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. And so first we need to recall from way back in some of our previous lesson videos that before a cell can actually divide. It's critical that the DNA must be replicated. Now this term replicated has a few synonyms that can be commonly used by your professors or in your textbook. And so the term replicated is synonymous with the term synthesized and or duplicated. And so DNA replication, DNA synthesis and DNA duplication all mean the same thing. And so we can say that this process of DNA replication is a process that produces an exact copy of all of the D. N. A. Inside of a cell. And so again this is critical for a cell to do before it actually divides. Because when a single cell divides into two separate cells, each of those cells needs a copy of the D. N. A. And that can only happen if DNA replication happens first. Now this process of DNA replication is going to convert unrepresented chromosomes or chromosomes that have not yet been replicated into replicated chromosomes or chromosomes that have gone through DNA replication. And so these replicated chromosomes that have gone through DNA replication are going to have two identical sister. Chroma tides. Now, the term sister here is really just used to imply that these chroma tides are identical to one another in terms of their D. N. A sequence. And the term chroma tied can really just be defined as half of a replicated chromosome. And the chroma tides are going to be joined to one another or one Chroma tide can be joined to another. Chroma tied at a region called the centrum ear. And so the central mere can really just be thought of as the waist position of the chromosome. And so we'll be able to see where the central here is in our image down below. And so if we take a look at our image, notice on the left hand side over here, what we're showing you is a single unrepresented chromosome. And so notice that this single un replicated chromosome kind of looks like a straight line uh here in this image. Uh and we can also think of a single unrepresented chromosome as just one chroma tied. Again, one chroma tide can be thought of as half of a replicated chromosome now notice this gray arrow here represents the process of DNA replication which is going to make an exact copy of this chromosome. And so after DNA replication, notice on the right hand side, what we have is a single replicated chromosome. And so again, this replicated chromosome has gone through the process of DNA replication. And so what you'll notice is that our unrepresented chromosome again is right here highlighted. And uh with this replicated chromosome we still have that same unrepresented chromosome is pressed. However, you'll notice that the unrepresented chromosome has been replicated. So over here, what we have is another identical copy of the pink highlighted region. And so what we call these regions, Okay, we call this and this. We call them chroma tips. And so uh these two here we can say they are too identical chroma types. Or in other words, they are sister chroma tides. And what you'll notice is that this uh sister cremated and this sister chromatic are attached to each other at this one position right here that we call the centrum ear. And so again, the centrum ear is almost like the waist position of a chromosome where the two sister chroma tides will be joined. And so this is a critical uh information because we can we can tell if a chromosome has gone through DNA replication because if the chromosome uh some what looks like an X. As you see over here, then we know that it's gone through DNA replication. But if the chromosome does not look like an X and it looks more like a straight line, then we can say that it is an unrepresented chromosome that has not yet gone through DNA replication. And so that can be very helpful information to note as we move forward and talk more about cell division but for now this year 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.