An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion is when the chromosome breaks at two points in a chromosome (or at the end) and does a 180 degree flip. The genes inside the inversion are in the reverse order.
Both chromosomes the same [change]
If both chromosomes of a pair have the same inversion, and there is no extra or missing genes, then there is no problem with meiosis.
Inversion on one chromosome only [change]
When the homologous chromosomes pair in prophase I of meiosis, the genes on the chromosomes pair up. The only way this can happen after an inversion is if the homologous pairs form a loop. If a cross-over occurs within this inversion loop, it can lead to loss or gain of DNA. For this reason, people with inversions in their germ cells often have lower fertility. This is because the gametes (eggs or sperms) are damaged.
Families that are carriers of inversions may be offered genetic counselling and testing.
- Gardner R.J.M. and Sutherland G.R. 2004. Chromosome abnormalities and genetic counseling. Oxford.