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Describe the processes that take place during each stage of mitosis.

During prophase chromatin condenses and supercoils, and so the chromosomes become visible. The nuclear envelope breaks down and the centrioles migrate to opposite poles of the cell and start to produce the s...
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Answered by Niamh C. • Biology tutor
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How are membranes classified according to their permeability?

An impermeable membrane is one through which no substance can pass. Semipermeable membranes are those which only let solvents, such as water, pass through them. Permeable membranes are those which let solven...
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Answered by Adam M. • Biology tutor
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Explain semi-conservative DNA replication, identifying the key enzymes involved and summarising their functions.

The DNA double helix structure, proposed by Watson and Crick in 1953, was the basis of the hypothesis that DNA replicated in a semi-conservative manner. In 1958 the Meselson-Stahl experiment supported this i...
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Answered by Jan D. • Biology tutor
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Explain the role of the pancreas in controlling blood glucose levels when they are too high.

Blood glucose levels increase after the consumption of carbohydrates. To answer this question, it is important to understand how the pancreas works. The pancreas is an organ that releases hormones - it is an...
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Answered by Krishna P. • Biology tutor
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Cystic fibrosis is an autosomal recessive condition. In a population, 0.04% of individuals have the disease. Use the Hardy-Weinberg equation to calculate the number of carriers of cystic fibrosis.

Autosomal recessive means that 2 copies of a allele are required for the phenotype. The phenotype is the set of observable characteristics due to the genotype. In this case the phenotype is whether an indivi...
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Answered by Caitlin N. • Biology tutor
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