Ormally, crossing over occurs between homologous regions of homologous chromosomes. sometimes mistakes happen, and crossing over occurs between nonhomologous regions of homologous chromosomes, resulting in duplications and deletions. what characteristic of a chromosome would make nonhomologous recombination more likely

Chromosomes that have little duplicated regions within them or similarities in their sequences

Explanation:

although non-homologous recombination does not requires homologous regions, it  typically utilize short homologous sequences or similarities in their sequences which result in mismatched alignments.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.