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(Redirected from Haplo-diploid sex-determination system)
The 'Haplodiploid sex-determination system' determines the sex of the offspring of many Hymenopterans (bees, ants, and wasps), and coleopterans (bark beetles). It may help to explain the evolution of eusociality in these species.
Several models have been proposed for this system. The model most commonly referred to is the ''complementary allele model''. According to this model, if an individual is heterozygous for a certain allele, it develops into a female, whereas hemizygous and homozygous individuals develop into males. In other words, diploid offspring develop from fertilized eggs, and are normally female, while haploid offspring develop into males from unfertilized eggs. Diploid males are infertile, as their sperm do not undergo meiosis, which means that their offspring would be triploid. This also means that Hymenopterans may be especially sensitive to inbreeding, as inbreeding reduces the number of different sex alleles present in a population, hence increasing the occurrence of diploid males.
After mating, fertile Hymenopteran females store the sperm in an internal sac called the spermatheca. She controls the release of stored sperm from within the organ: If she releases sperm as an egg passes down the oviduct, the egg is fertilized. ^[1]

Contents

Sex-determination in honey bees

References

See also

Sex-determination in honey bees

In honeybees the drones (males) are entirely derived from the queen, their mother. The queen has 32 chromosomes and the drones have 16 chromosomes. Drones produce genetically identical sperm. Males do not contribute to males - therefore males have no fathers or sons. The genetic makeup of the female worker bees is half derived from the mother, and half from the father.
^[2]
Thus, if a queen bee mates with one drone, any two of her daughters will share, on average, 3/4 of their genes. The diploid queen's genome is recombined for her daughters, but the haploid father's genome is inherited by his daughters "as is".
While workers can lay unfertilized eggs that become their sons, haplodiploid sex-determination system is beneficial to the individual due to indirect selection. The worker is more related to the queen's daughters (her sisters) than to the workers' sons (her nephews). Helping the queen's offspring to survive is aiding the spread of the same genes that the worker possesses
^[3]
Batches of worker bees are short lived and are constantly being replaced by the next batch, so this kin selection is possibly a strategy to ensure the proper working of the hive. However, since queens usually mate with a dozen drones or more, not all workers are full sisters. Due to the separate storage of drone sperm, a specific batch of brood may be closer related than a specific batch of brood laid at a later date. Kin selection may explain the evolution of these eusocial colonies.
'Shared gene proportions in haplo-diploid sex-determination system relationships'

Sex	Daughter	Son	Mother	Father	Full Sister	Full Brother	Niece/Nephew
Female	1/2	1/2	1/2	1/2	3/4	1/4	3/8
Male	1	0	1	0	1/2	1/2	1/4

References

1. van Wilgenburg, Ellen; Driessen, Gerard & Beukeboom, Leo W. Single locus complementary sex determination in Hymenoptera: an "unintelligent" design? Frontiers in Zoology 2006, 3:1
2. Sinervo, Barry Kin Selection and Haplodiploidy in Social Hymenoptera 1997
3. Foster, Kevin R.; Ratnieks, Francis L. W. The Effect of Sex-Allocation Biasing on the Evolution of Worker Policing in Hymenopteran Societies The American Naturalist, volume 158 (2001), pages 615–623


★ Unusually High Recombination Rate Detected in the Sex Locus Region of the Honey Bee (Apis mellifera) Martin Beye, Greg J. Hunt, Robert E. Page, M. Kim Fondrk, Lore Grohmann, and R. F. A. Moritz; Genetics (journal), Vol. 153, 1701-1708, December 1999

★ Single-locus complementary sex determination absent in Heterospilus prosopidis (Hymenoptera: Braconidae) Z. Wu, K. R. Hopper, P. J. Ode, R. W. Fuester, M. Tuda and G. E. Heimpel; Heredity (2005) 95, 228–234

★ Sex determination in the Hymenoptera Michael Mahowald, Eric von Wettberg; 1999

★ Reproductive harmony via mutual policing by workers in eusocial hymenoptera Francis Ratnieks; American Naturalist 132(2) 217-236 ; 1988

See also

★ Ploidy

★ X chromosome

★ Y chromosome

★ chromosome

★ sexual differentiation

★ Sex-determination system

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★ XY sex-determination system

★
★ ZW sex-determination system

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★ X0 sex-determination system