Practice question

An inversion arises when a chromosome breaks at two points and the intervening segment reinserts reversed, changing gene order 180 degrees. Classification depends on centromere position relative to breakpoints. If both breaks occur in same arm and the inverted segment excludes centromere, it is paracentric, meaning alongside centromere. Because centromere remains outside, crossover inside inversion loop produces dicentric bridge and acentric fragment causing inviability. Pericentric inversions include centromere and alter arm ratio. Breakpoint mapping and cytogenetic banding patterns distinguish types for clinical diagnosis and risk counseling.