Plants and animals use chemicals to co-ordinate metabolic activities and development. Tributyltin (TBT) is a commonly used chemical in boat building. The effect of TBT on the blood levels of two steroid hormones, testosterone and oestradiol, was investigated. Groups of male mice were fed corn oil alone, or corn oil containing different concentrations of TBT. The concentrations of testosterone and oestradiol in the blood of the mice was measured. The results are shown in the graphs. Describe how steroid hormones regulate gene transcription. (3) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................

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