Genetically, what is the effect of crossing over in the inversion loop?

Question

Genetically, what is the effect of crossing over in the inversion loop?

Answer 1

The effect of crossing over is variation.  

Answer 2

It depends on the location of the inversion relative to the centromere. If the  centromere is within the inverted area (paricentric inversion), and the crossover takes place within the inversion loop, then resulting chromosomes will have deletions and additions.

If you have a paracentric inversion (centromere outside the inversion) then  a crossover within the loop will result in a dicentric bridge and a small acentric fragment (chromosome with no centromere). As the acentric fragment has not centromere, it will be lost as it cannot segregate.

In either case crossovers outside the inversion loop proceed as normal.

I taught a tutorial on this material for years. One trick that worked really well is to get 2 colours of plasticine and use them to make chromosomes. Make inversions (both paracentric and paricentric) and do crosses to get a feel for what happens. I know this sounds juvenile, but it does work.