<prompt> The hormonal factor responsible for circadian rhythm is formed from which amino acid?TyrosineTryptophanPhenylalanineHistidine  <response>: Ans. is b i.e., Tryptophan In circadian rhythm maintenance melatonin is involved which is derived from tryptophan.Tryptophan is a precursor for synthesis of niacin nicotinic acid, serotonin and melatonin. 