Practice Questions

TLS Online TPP Program

#Question id: 41073

Q. A researcher is studying a novel receptor kinase involved in cell signaling. The functionally active form of this receptor is a homodimer that forms at the cell membrane upon ligand binding. The researcher isolates a mutant allele that produces a structurally altered, kinase-dead version of the receptor. When a heterozygous cell line (carrying one normal allele and one mutant allele) is generated, signaling is almost completely abolished, mimicking a null phenotype. Biochemical analysis reveals that the mutant protein is stably expressed and still binds to the normal protein.
which of the following best explains this observation?

#Unit 8. Inheritance Biology

The mutant allele is recessive, and the wild-type allele is unable to provide sufficient function due to haploinsufficiency.
The mutant protein acts as a dominant-negative by forming a dysfunctional complex with the normal protein, thereby poisoning the signaling pathway.
The mutant allele undergoes nonsense-mediated decay, leaving only the normal protein, which requires a higher concentration to function.
The mutant protein acquires a completely new, independent function (neomorphic gain-of-function) that suppresses all cellular signaling.