Question

If a gene undergoes duplication and one of the duplicated copy is mutated to render unexpressed protein. What will be the effect on phenotype?

(a) Mutant phenotype

(b) Normal phenotype

(c) Expression of the mutant gene is less than that would occur if both copy active

(d) The gene not expressed at all

The question was asked in an international level competition.

The query is from Chromosomal Abnormalities : Duplication in portion Chromosomal Basis of Inheritance of Cytogenetics

Answer 1

The correct answer is (b) Normal phenotype

The best I can explain: In this case as the product of the 2^nd copy is mutated and not affecting the phenotype, only one copy is producing the required product in normal quantity. This is similar to the duplication being silenced.