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Biology
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Vaccines have become an effective way to prevent certain diseases, however for some viruses it is difficult to develop a vaccine. Describe possible difficulties of developing a permanent vaccine for the influenza virus.

The influenza virus has a very high mutation rate. This means that its surface proteins (antigens) will change. Since a vaccine contains a specific antigen, if the virus switches to a different antigen, t...

Answered by Nancy L. Biology tutor
2078 Views

Explain the stages of the cardiac cycle

The cardiac cycle consists of series of chamber systole and diastole. Systole is the name given to a period when cardiac muscle contract to cause blood ejection from the respective chamber to another. Dia...

Answered by Aliaksandra B. Biology tutor
14907 Views

Give one piece of evidence that supports the theory that mitochondria evolved from prokaryotic cells. (1 mark)

Size: mitochondria are 2uM in diameter, similar to bacteria. Also applies to genome size and content, suggesting an 'endosymbiosis' event.

Answered by Lauren M. Biology tutor
6686 Views

How does DNA lead to the production of proteins?

Proteins are encoded by the information stored in the DNA genetic material. This happens in two stages: transcription and translation. During transcription, the DNA unravels and exposes it's sequence, all...

Answered by Millie S. Biology tutor
2588 Views

What is an enzyme? Explain their importance?

Enzymes are specific proteins that catalyse a specific reaction or breakdown of a substance. They allow a variety reactions to take place without using as much energy (improve efficiency). Useful to think...

Answered by William W. Biology tutor
2230 Views

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