Haplodiploid sex-determination system
From Wikipedia, the free encyclopedia
The Haplodiploid sex-determination system is a system that some Hymenopterans (bees, ants, and wasps), and coleopterans (bark beetles) use to determine the sex of their offspring, and preserve eusociality. In this system, there are no sex chromosomes. Instead, the sex is determined by the number of chromosomes. Haploid offspring (which are from unfertilized eggs) are males, while Diploid offspring (which are fertilized eggs) are females.
[edit] 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. 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. 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". Drones produce genetically identical sperm.
Although the queen lays eggs with a 1:1 sex ratio, the worker bees manipulate the offspring so that a sex ratio of 3:1 (females to males) is preserved. They do this by an action known as worker policing, wherby they will eat any unfertilised eggs laid by fellow workers. This is beneficial to the individual due to indirect selection - since 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 (Ratnieks 1988).
The worker bees are short lived and are constantly being replaced, so this kin selection is possibly a strategy to ensure the proper working of the hive.
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 | 1/2 | Males do not contribute genes to sons only to daughters | 1 | Males do not have fathers | 1/2 | 1/2 | 1/4 |
[edit] References
- Kin Selection and Haplodiploidy in Social Hymenoptera Barry Sinervo, 1997
- 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
- Single locus complementary sex determination in Hymenoptera: an "unintelligent" design? Ellen van Wilgenburg , Gerard Driessen and Leo W Beukeboom; Frontiers in Zoology 2006, 3:1
- 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
[edit] See also
 |
This genetics article is a stub. You can help Wikipedia by expanding it. |
 |
This biology article is a stub. You can help Wikipedia by expanding it. |
