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Biology

A Level

What is the difference between DNA and RNA?

DNA and RNA are both examples of nucleic acids, and so are formed from long chains of nucleotides. However, there are three broad structural differences between the two. 1) DNA is usually found double-str...

Answered by Luke K. • Biology tutor

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What is the function of T-helper cells?

T-helper cells are a kind of lymphocyte that are a key part of the adaptive immune system. The adaptive immune system is largely coordinated by T cells, of which there are several types, and B cells, the ...

Answered by Theo F. • Biology tutor

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Explain the Cardiac Cycle

Deoxygenated blood from the body drains into the right atrium of the heart through the superior and inferior vena cava blood vessels. The blood then travels from the right atrium, through the tricuspid va...

Answered by Simi P. • Biology tutor

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Mutations of a DNA sequence could alter the expression of a gene. Describe and explain the process of gene expression and how a mutation could lead to disease.

DNA is a universal code for all living beings known to man. There are four nucleotide bases in DNA and RNA, the combinations of these sequences are what determine the order and length of a polypeptide. Ev...

Answered by Omar S. • Biology tutor

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How can natural selection and isolation lead to speciation?

What is speciation?When a new and distinct species evolves from an ancestor speciesReproductively isolated from the ancestor/other species2. How does natural selection work?a. Population of individuals, w...

Answered by Laura P. • Biology tutor

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