Inversion polymorphism in a Connecticut river Axarus species (Diptera: Chironomidae): biometric effects of a triple inversion heterozygote. Canadian Journal of Zoology 82: 118-129.
M/A= inversion heterozygote. M/M = metacentric inversion homozygote.
There is no phenotypic effect in the majority of pericentric inversion heterozygote
carriers with balanced rearrangement.
If the inverted region is large enough, the homologous chromosomes in an inversion heterozygote
pair gene by gene and form a loop configuration that can be observed at pachytene.
Diakinetic nuclei were examined for the frequency of chiasmata (bivalent/trivalent formation) and for frequency and incidence of crossing over within the inverted region of pericentric inversion heterozygotes
. To estimate the relative frequency of nondisjunction and malsegregation, secondary spermatocytes (metaphase II cells, MII) were scored for the number of metacentric and acrocentric macrochro-mosomes and presence of either the Y or two X chromosomes.