This suggests that the new locus is a functional gene. Chromosomal alterations Many chromosomal alterations produce larger-scale gene changes, relative to the other types of mutations we have been discussing. A. Chromosome inversions Inversions occur when a chromosome segment breaks in two places, flips, and reanneals in the inverted orientation. Inverted sequences do not align properly with their normal homolog during synapsis, so successful crossing-over events within an inverted sequence are rare. The alleles within an inverted sequence tend to be so tightly linked together that they are inherited as a single supergene.
Inversions are common in insects.
For example, Drosophila subobscura, a fruit fly with 6 chromosomes. Five of the chromosomes are polymorphic for at least one inversion. The New World populations rapidly spread along the coast of each continent. This is a large-scale chromosomal mutation, in which entire sets of chromosomes are duplicated. Polyploidy can result from a number of different events, including errors during meiosis leading to diploid gametes.