Zoology - Principles of Inheritance and Variation Question with Solution | TestHub
Read the following properties about two diseases phenylketonuria and alkaptonuria:
| Properties | Phenylketonuria | Alkaptonuria |
| Type | Autosomal recessive disease | Autosomal recessive disease |
| Defective gene | p | a |
| Location of the defective gene | Chromosome 12 | Chromosome 3 |
| Enzyme deficient in the defective gene | Phenylalanine hydroxylase | Homogentisic acid oxidase |
| The function of enzyme in a normal person | Conversion of phenylalanine to tyrosine | Conversion of homogentisic acid to maleyl acetoacetic acid |
| Urine | Phenylketone is excreted in urine giving it a musty odour | Alkapton is excreted in urine giving it black colour when exposed to air |
In our body tyrosine is the only precursor for the formation of homogentisic acid.
Rohit has genotype aapp. His urine will
Options:
Answer:
Solution:
The two genes are present on two different chromosomes so they will be independently assorted. Rohit has genotype aapp. It means in his body both phenylalanine hydroxylase as well as homogentisic acid oxidase is not produced. Phenylalanine hydroxylase enzyme converts phenylalanine to tyrosine. So in Rohit's body tyrosine will not be formed. Phenylalanine will accumulate in his body and will produce phenylketone. Since tyrosine is not formed in the body of a person suffering from phenylketonuria, homogentisic acid will not be formed and there won't be any symptoms of alkaptonuria.
