These species allowed a more profound understanding of B-chromosome meiotic behavior, including mechanisms of elimination and accumulation through meiotic drive
, B chromosome structure in terms of molecular composition, effects on carriers at the endo- and exophenotypic levels, distribution in natural populations, including cases of clinal variation, and the relationships of Bs with the A genome and their evolution through genomic conflict, especially in E.
Control of meiotic drive
of B chromosomes in the mealybug Pseudococcos affinis (obscurus).
Because asymmetric distribution of centromeric activity in structural heterozygotes has the potential to select for chromosomal variants through meiotic drive
(Pardo-Manuel de Villena & Sapienza, 2001), increased rate of centromere evolution may lead to higher rates of fixation of chromosomal variants.
This is not surprising, because cycles of cell fusion and chromosome segregation provide very strong selective advantages to molecular parasites, such as transposable elements and meiotic drive
genes, which have clearly modified the sexual process to further their own interests.
The t haplotypes of the house mouse were first discovered in 1927 (Dobrovolskaia-Zavadskaia and Kobozieff 1927), and remain one of the best studied mammalian examples of meiotic drive
, or ultraselfish DNA (Wu and Hammer 1991).
There is no reason to suppose that the incidence of segregation distortion is limited to only a few species, and, indeed, meiotic drive
may be quite common.
The curious phenomenon of meiotic drive
occurs when a genetic component is transmitted through generations more often than would be expected under accepted genetic laws.
Genotypes suppressing meiotic drive
of a B chromosome in the mealy bug Pseudococcus obscurus.
Sex-ratio meiotic drive
is not a literal model of X-chromosome evolution in human beings, but a model of how non-Mendelian segregation can offset strong selective forces at the zygotic level.
for B-chromosomes in the primary oocytes of Myrmeleotettix maculatus (Orthoptera: Acrididae).
Therefore, the most likely mechanism for B accumulation is meiotic drive
The persistence of this chromosome change would have been facilitated considerably by either a modification in sex ratio or some form of meiotic drive