Question

Which one is a hereditary disease/ mendelian disorder?
 A. Cataract
 B. Leprosy
 C. Blindness
 D. Phenylketonuria

Answer 1

Hint: Genetic disorder that occurs when the human body is unable to make use of the essential amino acid to breakdown Phenylalanine.

Complete Answer:
A) Cataract is caused due to the cloudy deposition on the lens of your eye. Aged people and people subjected to high radiation exposure are in the risk zone of getting affected.
B) Leprosy is the first bacterial infectious disease. It is caused by Mycobacterium leprae. It affects the peripheral nerve, skin and muscles with lesions and big lumps.
C) Blindness can occur due to many reasons some of which include blind from birth while some may be due to accidents that occur in a person’s life.
D) Phenylketonuria also known as PKU is a hereditary disorder that occurs when the gene that helps in creating the enzyme needed to break down the phenylalanine is defective.

Thus the correct option is D) Phenylketonuria.

Additional Information:
- PKU was discovered by Norway physician Asbjorn Folling in 1934. It is an Autosomal Recessive disease. Normally phenylalanine is converted to tyrosine which is the precursor for melanin and dopamine.
- Absence of phenylalanine hydroxylase enzyme prevents conversion of phenylalanine to tyrosine which results in excess phenylalanine amino acid accumulation in the human body.
- Clinically children develop vomiting, eczema like rashes and musty odour urine and body fluids. When progressed children develop mental retardation and seizures. Patients with PKU are advised to follow a low protein diet for a lifetime.

Note: Hereditary Disorder occurs through defective genes that are passed on from one generation to another generation in the same family. No external triggers or microorganisms can cause the genetic disorder.