Question

Absence of Phenylalanine hydroxylase in the liver produces a disease called.
(a)Alkaptonuria
(b)Phenylketonuria
(c)G6-PD deficiency
(d)Duchenne’s muscular dystrophy

Answer 1

Hint: This is an inherent disorder that increases the level of Phenylalanine in the blood. It is found in all foods having protein and is also found in few artificial sweeteners. The presence of an excess of phenylalanine may cause an odor in the skin and the mouth. This disease has symptoms that include seizures and eczema. Also, it hinders mental development.

Complete answer:
The disease is an inherent one and is caused due to mutation in the gene of Phenylalanine hydroxylase. The Phenylalanine hydroxylase or PAH gene is responsible for the production of Phenylalanine hydroxylase. PAH is used to convert the amino acid named Phenylalanine to be broken down into simpler compounds. The absence of the PAH results in an abnormally high level of Phenylalanine in the blood, hence all patients suffering from PAH deficiency are suggested a diet devoid of protein. Now, if you look at the options given the option which satisfies the above facts is the disease Phenylketonuria, because Alkaptonuria is caused due to accumulation of Homogentisic Acid, G6-PD is associated with the breakdown of RBCs, and Duchenne’s muscular dystrophy is muscular weakness, unrelated to Phenylalanine.

Additional Information: It will always be beneficial for you to know about some extra points on the other options that are given in the question. Some information regarding the other options are as follows:
-Alkaptonuria: It is a metabolic disorder caused due to the accumulation of Homogentisic acid in the human body. Patients suffering from Alkaptonuria are unable to break down the Homogentisic acid which ultimately leads to its build-up. Its symptoms include the passing of dark-colored urine or urine which transforms into black when comes in contact with air.
-G6-PD deficiency: It is mostly a male genetic disorder having insufficient levels of an enzyme termed as glucose-6-phosphate dehydrogenase (G6-PD). The working of the RBCs is aided by the G6-PD and also protects the RBCs from any harmful substance that might be present in the blood.
-Duchenne’s muscular dystrophy: It is a congenital condition that tends to affect the muscles of the patient. It leads to the wasting of muscles which worsens the age of the patient. Male subjects are known to be most affected by this disease, causing loss of cardiac and skeletal muscles.
So, the correct answer is, “Phenylketonuria”.

Note: -All diseases mentioned here are genetic disorders, hence you must deduce the correct option from the disease characteristics given in the question.
-Phenylketonuria also causes brain damage too and hence could also be associated with such types of questions too, therefore you must know the characteristics of diseases because option elimination may not be possible in some questions.