Question

Person ‘A’ is suffering from an inborn error of metabolism due to an autosomal recessive trait. This error results mental retardation in him. Person ‘B’ also have retarded mental development but in this person it is due to trisomy of a particular chromosome.

Select the correct option regarding person ‘A’ and person ‘B’.
[0.7 mark]

• A.

  Person 'A'	Person 'B'
  The responsible gene is located on two non-homologous chromosomes	The disorder is a Mendelian disorder

• B.

  Person 'A'	Person 'B'
  This person lacks a particular pancreatic hormone	This person has three X-chromosomes

• C.

  Person 'A'	Person 'B'
  Defective haemoglobin is forming in this person	This person is sterile female

• D.

  Person 'A'	Person 'B'
  This person is unable to convert phenylalanine into tyrosine	This person has trisomy of chromosome 21

Answer 1

The correct option is D

Person 'A'	Person 'B'
This person is unable to convert phenylalanine into tyrosine	This person has trisomy of chromosome 21

Person ‘A’ is suffering from phenylketonuria. It is an inborn error of metabolism. In this disorder, the affected individual lacks a liver enzyme that converts phenylalanine into tyrosine. This results in mental retardation.

Person ‘B’ is infected with Down’s syndrome. It is due to trisomy of chromosome 21. Mental development is also retarded in this.