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Biology
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Describe the cardiac cycle (7 marks)

During diastole the atria and ventricles are relaxed. The atrioventricular valves are open and the semilunar valves are closed. Deoxygenated blood enters the right atrium from the venae cavae and oxygenat...

TS
Answered by Tara S. Biology tutor
15594 Views

How do electrical impulses control contraction of the heart?

Electrical impulses from the SAN (sinoatrial node) spread across the atria walls to cause contraction. The impulses then pass to the ventricles via the AVN (atrioventricular node) after a short delay to a...

JA
Answered by Jack A. Biology tutor
2246 Views

Explain the concept of recessive and dominant alleles

Firstly it is always good to relate such a concept with an example that is easily remembered and therefore easily applied. Alleles refer to alternate forms of the same gene, which code for a particular tr...

JC
Answered by Juliette C. Biology tutor
4712 Views

Why is an action potential an all or nothing process?

An action potential is the signal neurons use to communicate with each other. It is caused by the rapid opening of sodium channels and influx of sodium ions. Because at rest the inside of the neuron is ne...

GG
Answered by Gemma G. Biology tutor
7496 Views

Explain what happens when there is a mutation in a gene whereby 2 bases are deleted ?

As there are 2 bases which are deleted a frameshift will occur at the site of the mutation. This means that all other amino acids coded for by the genes after the point of mutation will be different. This...

KT
Answered by Kevin T. Biology tutor
2922 Views

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