Pseudo-arrhenotoky or paternal genome elimination is the phenomenon where males develop from fertilized eggs but the paternal genome is

heterochromatin Heterochromatin is a tightly packed form of DNA or '' condensed DNA'', which comes in multiple varieties. These varieties lie on a continue between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role ...

ized or lost in the somatic cells and not passed on to their offspring. This phenomenon occurs in certain

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s and

mealybug Mealybugs are insects in the family (biology), family Pseudococcidae, unarmored scale insects found in moist, warm habitats. Many species are considered pest (animal), pests as they feed on plant juices of greenhouse plants, house plants and sub ...

s and

scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...

s. When the males have a diploid number of chromosomes they are termed ''parahaploids'' as the paternal genes are not expressed at all. The paternal chromosomes are inactivated by heterochromatization in all the cells at an early embryonic stage. The adult cells have one set of inactive ''H chromosomes'' and one set of euchromatin ''E chromosomes''. These H chromosomes are eliminated from the sperm during or just before spermatogenesis. In a few other species all the cells in an adult are haploid due to elimination of the paternal chromosomes at an early developmental stage. This variant is called the ''diaspidid system'' after the

clade (

Diaspididae Diaspididae is the largest family of scale insects with over 2650 described species in around 400 genera. As with all scale insects, the female produces a waxy protective scale beneath which it feeds on its host plant. Diaspidid scales are far mo ...

) where it was discovered. It is also found in some mites. Genetically this system is equivalent both to

haplodiploid Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the se ...

arrhenotoky Arrhenotoky (from Greek -τόκος ''-tókos'' "birth of -" + ἄρρην ''árrhēn'' "male person"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthe ...

where the males are haploid and develop from unfertilized eggs and to certain cases of diploid arrhenotoky where the males get a diploid chromosome set from their mother but inactivate and fail to pass on half of them. Pseudo-arrhenotoky causes a female's genetic contribution to her son's children to double. This

intragenomic conflict Intragenomic conflict refers to the evolutionary phenomenon where genes have phenotypic effects that promote their own transmission in detriment of the transmission of other genes that reside in the same genome. The selfish gene theory postulates ...

between maternal and paternal genes can lead to pseudo-arrhenotoky arising. Under conditions where the optimal sex ratio is biased, pseudo-arrhenotoky allows the female a precise control of the ratio of sons to daughters. Pseudo arrhenotoky has evolved into

y (haploid

) in some species possibly due to sustained intragenomic conflict or due to pressure to colonize habitats by a single unmated female. Relative to arrhenotoky, pseudo-arrhenotoky may have the advantage of allowing DNA damage to be repaired.

References

{{Reflist Reproduction in animals Sex-determination systems

See also

References