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.
<span>They capture energy from sunlight and manufacture their own food</span>
Answer:
Ischemic heart disease
Explanation:
Ischemic heart disease is a condition of recurring chest pain or chest discomfort that happens when a part of the heart does not receive enough blood.
This happens when the arteries have become blocked with plague and blood can no longer reach the arteries.
In cases where medication fails, surgical procedure like CORONARY HEART BYPASS is done. This is when blood flow is routed by arteries transplant, this procedure helps to restore blood flow.
Answer:
Which of the following is a complementary base pair ?
A . guanine - thymine
B . guanine - guanine
C . adenine - cytosine
D . guanine - cytosine
Explanation:
