Correct option is D
Explanation-
A chromosomal inversion involves two breakpoints where the DNA is cut and reinserted in reverse. If a breakpoint occurs within an essential gene, it can Interrupt the gene’s coding sequence, damage regulatory regions and can cause loss of function or non-functional proteins. Especially harmful if it involves genes critical for development or cell function
Therefore, when the question asks what the breakpoint disrupts, this is the most direct and harmful effect.
Incorrect options-
Option a : Pairing of the homologous chromosomes
In heterozygous condition (one normal chromosome, one inverted), pairing problems do occur during meiosis. The chromosomes form an inversion loop to align properly. This can cause reduced recombination, duplications, deletions. But The pairing issue is a consequence of the inversion, not of the breakpoint itself. The breakpoint disrupts sequence continuity, not pairing directly. This is partially true, but not the best answer to what the breakpoint itself disrupts.
Option b : A non-coding region of the genome
Breakpoints can occur in non-coding regions, and if they do, disruption may be minimal or none. Non-coding regions don’t usually have functional genes, unless they’re regulatory regions (enhancers, promoters). This is not a guaranteed disruption, and certainly less damaging than hitting an essential gene. This is not a reliable or specific disruption caused by breakpoints.
Option c: A coding region of the genome
This seems plausible: if a breakpoint lands in a coding region, it can disrupt gene function. However, the question adds: "a gene with an essential function", which is more specific and severe. A coding gene that is not essential may be disrupted without major phenotypic effects.
So, this is close, but Option d is more precise and correct.
Final Answer: Option d – A gene with an essential function
