Animal Viruses: Antigenic Drift vs. Antigenic Shift

in this video, we're going to continue to talk about animal viruses and animal virus infections by specifically focusing on anti genic drift and anti genic shift. And so first we need to recall from some of our previous lesson videos that the enzyme replicates, which recall is an RNA dependent RNA polymerase used by RNA viruses actually has no proof reading ability. And so recall from some of our previous lesson videos that proof reading is an ability used by preliminary races to fix any mistakes that it may have made and to avoid mutations. However, the enzyme replicates has no proof reading ability, which means that it's going to allow for mutations to accumulate over time. And this accumulation of mutations over time can lead to what is known as anti genic drift. And so anti genic drift is really just genetic variations or genetic changes over time that is resulting from mutations that are caused by a lack of proof reading ability in the enzyme replicates. And so over time these genetic variations, these genetic changes can result in fen a typical changes or the changes of observable characteristics and traits in the virus. And so this anti genic drift can allow viruses to avoid the immune system responses by a host cell, allowing the virus to adapt and to uh basically be able to reproduce at a more effective rate. Mhm. And so this is uh anti genic drift is really part of the reason why it is recommended that you get the flu vaccine every single year because the influenza virus that causes the flu is actually an RNA virus and the replicates enzyme which lacks proof reading ability allows for mutations to accumulate in the influenza virus leading to genetic variations. And so the flu virus is able to avoid the immune response over time. And so that's why we need updated flu vaccines every year to protect us from the influenza virus, which changes due to anti genic drift. And so if we take a look at our image down below, over here, on the left hand side, it's focusing on anti genic drift. And so notice over here on the left hand side, we're showing you a virus and this is virus A. And this is an RNA virus and over time the replicates enzyme which does not have proof reading ability allows for the accumulation of mutations over time. And so you can see that virus A accumulates mutations and this mutation right here, you can see here is in red and so this changes virus A. To become a different strain of the virus virus B. And so the characteristics that result from this mutation can allow this virus to avoid host immune responses. And so anti genic drift is really just changes genetic changes in the virus due to mutations over time. Now, in addition to genetic drift, there's also something known as anti genic shift. In addition to angiogenic drift, there's also antigenics shift. And so some RNA viruses can actually have more than one piece of RNA from different viruses which can cause what we know as anti genic shift. And so anti genic shift is really going to result from the formation of a new virus subtype that has R. N. A. From multiple viruses. And so if we take a look at our image down below notice we're focusing on anti genic shift and so notice that we actually have two RNA viruses here we have virus A. And we have virus B. And if virus A. And virus be in fact the same cell at the same time and enter the host cell at the same time. What can happen occasionally is the mixing of the RNA from the two viruses to create a new virus that we have here which is virus C. And so notice that the new virus has some RNA. Here that was originating from virus A. And it also has some RNA. Here that was originating from virus B. And so the mixing of the R. N. A. Creates a new virus and we call this anti genic shift. And so this here concludes our brief introduction to anti genic drift and antigenics shift and we'll be able to get some practice applying these concepts and learn more about animal viruses as we move forward in our course. So I'll see you all in our next video