The mice were bred to have malfunctioning immune systems, then injected with human cancer cells, which as a result, grew quickly into large tumours.

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For instance, Unilever scientists have spent five years working with yeast cells that replicate human taste receptors, and then extracting substances from food to see how they might trigger these receptors.

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He inserted the human form of this gene into hamster ovary cells, which then churned out a genetically engineered version of the hormone.

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Stem cells typically are taken from days-old human embryos and then grown in a laboratory into lines or colonies.

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