Question

Assume that for a given gene a mutation creates an allele that functions as a dominant negative. The gene codes for a protein that forms a tetramer (4) within the cell. If at least one of the subunits has the mutant structure the entire protein is inactivated. For a heterozygous individual, what percent of the tretramers present in the cell will be inactive?

Answer 1

As mentioned in the question, the mutation is creating a dominant mutation. Dominant mutation means that if atleast one copy of the dominant allele is present then the mutation will be expressed in the individuals. The gene is coding for a protein that forms a tetramer within a cell and if atleast one of the subunits has the mutant structure the entire protein is inactivated. For a heterozygous individual, single copy of the mutated allele is present in the individual which will make the protein inactive and hence because a single copy of the mutated allele is enough to show its phenotypic nature the entire protein will get inactivated. Hence for a heterozygous individual, the whole percent of the tetramers present in the cell will be inactive.

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