Flu vaccines need to be revised and changed every year because the flu virus constantly mutates. Flu viruses can change in two ways: drift or shift. Antigenic drift occurs when genes of the virus slowly change during replication until the immune system no longer recognizes it. On the other hand, antigenic shift occurs when a major change in the virus happens. This usually leads to a totally different kind of virus. This is what happened during the H1N1 scare in 2009.
DNA viruses like mumps are less prone to mutation due to the presence of DNA polymerase. RNA viruses are more prone to mutation because they undergo reverse transcription to simulate the role of DNA.
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is a principle of geology that states that the geologic feature which cuts another is the younger of the two features. It is a relative dating technique in geology.
The mitochondria breaks down food into molecules the cell can use.
Answer: I think maybe 3 times I don’t remember when I did this test but I think that’s the answer
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