Which mutation involves a piece of the chromosome flipping its orientation?

• A. Plastids
• B. Inversion mutation
• C. Frameshift mutation
• D. Nonsense mutations

Answer: (B)

Inversion mutation is a structural change where a segment of a chromosome breaks off, flips around, and reattaches in the opposite orientation. This reversal means the order of genes within that segment is inverted, even though the total amount of genetic material stays the same. Depending on where the breaks occur, it can disrupt genes at the boundaries or alter how they’re regulated, and during meiosis it can suppress recombination inside the inverted region, which can affect fertility or gamete outcomes. The other concepts you might see—such as plastids (organelles in cells), frameshift mutations (which shift the reading frame of a gene due to insertions or deletions), or nonsense mutations (a single change that creates a premature stop codon)—do not involve flipping a chromosome’s orientation, highlighting why inversion is the correct idea here.