The hormonal factor responsible for circadian rhythm is formed from which amino acid?
Tyrosine
Tryptophan
Phenylalanine
Histidine
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.