Chromosomal inversions occurs in one of the chromosomes where the head of the chromosome flips back on itself (forms a loop). Inversion can be advantageous or detrimental to the genetic code depending on where these inversions take place. These inversions take place during prophase of meiosis I (sometimes in metaphase and anaphase). These inversons can cause crossing over in part or none of the actual chromosome. There are two types of inversions that can occur: Paracentric and pericentric
Paracentric inversions does not occur in the centromere. Crossing over only occurs in the out The loop occur in one arm of the chromosome. The result is a large loop in where recombination occurs in only part of the loop. Dicentric bridges (two loops) can form in the center of the chromosome where recombination does not occur. An acentric loop also occurs in the centromere region. The result is recombination in one loop.
Pericentric inversion does occur in the centromere (in some cases). The most important part is that the chromosome can be elongated or shorted after the inversions have taken place. Deletions and duplications can occur during crossing over during the inversion. The result is recombination in two loops.