An inversion heterozygote forms an inversion loop during synapsis.

If crossing over does not occur within the inversion, segregation will produce a 1:1 normal:inverted ratio in the gametes, and 1/2 the offspring will inherit the inversion.

However, if crossing over does occur within the inversion loop, abnormal chromatids are produced, with reduced gamete viability. This is likely with large inversions.