Which statement is true regarding inversions?

Inversions are structural chromosomal alterations where a segment of the chromosome is reversed end to end. The statement that they only cause symptoms if the breakpoint is in a key gene is accurate because inversions can disrupt gene function if the breakpoints occur within or near an essential gene.

For instance, if an inversion occurs and involves the coding region of a gene, this can lead to no functional protein being produced or the production of a dysfunctional protein. Alternatively, if the inversion takes place in non-coding regions or between genes, it may not have any noticeable effect on the organism’s phenotype at all.

Other statements do not accurately capture the complexity of inversions. While some inversions can lead to abnormal phenotypes, it is not guaranteed that they will do so in every case. Likewise, while many inversions may be benign and not cause any clinical issues, this is not universally true. Lastly, while certain chromosomal abnormalities can lead to fertility issues, inversions do not inherently cause infertility in all individuals; their effects can vary widely depending on the specific genetic context and the genes involved.