Molecular Basis of Inheritance Practice Test

The key idea is that gene fusions across different chromosomes arise when parts of two separate chromosomes are swapped or joined. This happens with a chromosomal translocation, especially a reciprocal translocation, where segments from non-homologous chromosomes exchange places. When breakpoints occur in or near two genes on different chromosomes, the resulting fusion gene can be transcribed into a single chimeric mRNA and translated into a novel protein with combined features from both original genes. A classic example is the BCR-ABL fusion from a t(9;22) translocation in certain leukemias, which creates a constitutively active kinase that drives cancer.

Inversions rearrange DNA within the same chromosome and can disrupt genes or alter regulation but don’t inherently join genes from different chromosomes. Deletions remove material, and duplications copy material within the genome; neither by itself creates a fusion between genes on separate chromosomes.