mortality/aging
• homozygotes are born to heterozygous parents at 1/4 the frequency expected
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growth/size/body
• mutants begin gaining weight in the second month after birth and by the third month of age, they are about twice the weight of wild-type
• mice treated with a stable alpha-melanocyte-stimulating hormone agonist lost more than 40% of their excess weight in 2 weeks
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• the weight gain in accompanied by a slight, but significant, increase in body length
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• mutants show an increased rate of weight gain on a high fat diet
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pigmentation
• coat covering the sides and belly is more yellow than in wild-type and the tips of the hairs at the back have a more yellowish tinge
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endocrine/exocrine glands
homeostasis/metabolism
• mutants show an increased rate of weight gain on a high fat diet
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• serum corticosterone is below detectable levels
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• weight gain is accompanied by a large increase in serum leptin levels
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• serum aldosterone is below detectable levels
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• dopamine levels are slightly higher
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behavior/neurological
• mutants have a greater food intake than wild-type on both a regular or high-fat diet
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integument
• coat covering the sides and belly is more yellow than in wild-type and the tips of the hairs at the back have a more yellowish tinge
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