Chromosomal Rearrangements: Inversions

Hi in this video we're gonna be talking about inversions. Okay, so an inversion is when the chromosome keeps all the same genetic information but the order of it is switched around. So an inversion is when the orientation of a segment is reversed or flipped. Now there's gonna be two types. We have the para centric version and the perry centric version. Now these are really similar. So make sure you don't mix them up. P. A. And P. E. So para and perry. Now pere is going to not include central mirror. So inversion inversion that what happens outside of the central mirror? Perry includes the centrum ear. So when the segment that's being flipped also includes the centrum here. So let's look at the example. So if we had a chromosome here, we'll call it A. B. C. D. This is going to be our normal version. And it has a central here, right here. A para centric inversion is when the part that's being flipped, which in this case is C. And D. There's no central mirror, right? Like we can cut here and flip this um chromosome around and make it normal and we can cut there and flip it around and make it para centric, right? The D. N. C. We flip it around. There's no central air involved. Perry centric is when there is a central mere involved. So you can see that the C. And the B. They inverted supposed to be A. B. C. D. But instead it's a C. B. D. But this inversion includes the centrum here. So when it flips we have the center mir included. So that's the perry now. When this happens, what we usually get is we get one normal chromosome and then one inverted chromosome. Either para centric or peri. It doesn't matter often we get one normal one inverted. And what we call that is an inversion. Hetero zygote. Okay, we have one normal and one inverted. Now this hetero zygote, we typically think of actually referring to genes or leal's and we think hetero zygote. We see we think this right? One dominant and one recessive allele. But that is not what this means. Right? So if we look at these above, if we take this and this Or let me just write it again here. So if we have one chromosome that looks like this one normal and one that looks like this. Hold on, wrote that wrong. May write my letters correctly C. B. D. There we go. So if we have one normal and one paris centric, we can see that actually in this case all of the alleles are dominant. Right? We have to we have this homicide is dominant for both chromosomes. Right? So it's not that the alleles are hetero zegas, it's just that the chromosomes our heterocyclic. Now, how do inversions happen? Well a lot of times what happens to them is an inversion loop forms and an inversion loop literally kind of just looks like a ribbon. And you can see right here during this part. This section in this section can easily flip over. Okay. And sometimes you'll see it drawn like this. Right. And during this section you can imagine how easily it is for a gene that's here to get put really close to a gene that's here. Okay, so these are examples of inversion loops and that is what forms and what allows these inversions to take place. Okay, so the twisting of one end pairs with an un inverted one or pairs with an un inverted end. And that ends up causing inversions. Now, if scientists want to study inversions then what they often do or they want to study genes in general, not just inversions, just any kind of jeans. A geneticist wants to study that but they don't want any kind of crossing over. They really don't want to mess up with the gene. They really want to keep everything as stable as possible. One of the things that they will do is use a balance or chromosome now balance or chromosome is a chromosome that scientists have created. It contains a ton of inversions in it just in version after version after version. And the reason that it does is because it wants to prevent crossing over. So that suppresses crossing over so that scientists can study a gene or chromosome without crossing over occurring. So balancer chromosomes are inverted chromosomes that scientists have made to help in their studies. So here's an example of an inversion. Hetero zygote. We can see we have one normal chromosome, we have A. B, C. And D. In their correct order in the center meet here and we have one inversion, A C, B and D. Now note this is hetero zygotes referring to one normal and one inverted chromosome and has nothing to do with the alleles, which in this case are all homos I guess dominant. Okay, so make sure you don't mix that up because students get really confused about that because they hear hetero saiget and they're already thinking alleles in this case inversion. Hetero Z. Get focuses on chromosomes. Okay, so with that let's move on.

A person has a WT chromosome with the following segments. A B C • D E F G H. Which of the following shows how the chromosome would look after an paracentric inversion?

• A. A B C • D E F G H
• B. A B E D • C F G H
• C. A B C • D G H
• D. A B C • D G F E H

A person has a WT chromosome with the following segments. A B C • D E F G H. Which of the following shows how the chromosome would look after a pericentric inversion?

• A. A B C • D E F G H
• B. A B E D • C F G H
• C. A B C • D G H
• D. A B C • D G E F H