This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Biochemistry
Asians & native americans may flush & feel ill after drinking small amount of ethanol. This reaction is due to genetic variation in which enzyme: 
Select and explain. 
A. Alcohol dehydrogenase, B. Aldehyde dehydrogenase, C. Isocitrate dehydrogenase, D. Alpha-keto glutarate dehydrogenase
B: Aldehyde dehydrogenase
Answer: B: Aldehyde dehydrogenase 
Explanation: * Genetic variation occurs in enzyme aldehyde dehydrogenase, specially in people of China, Korea & native America, known as Asian flush syndrome. Increased acetaldehyde causes:- Nausea Vomiting Flushing Sweating Tachycardia & hyperventilation ADDITIONAL READING ON ALCOHOL DEHYDROGENASE (ADH): There are many isoenzymes Most abundant - ADH-1A Present in cytoplasm of liver and adrenal glands Has NAD containing domain known as Rossman fold