12-03-2004, 12:33 AM
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#10
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Quote:
Parthenogenesis
In parthenogenesis ("virgin birth"), the females produce eggs, but these develop into young without ever being fertilized.
Parthenogenesis occurs in some fishes, several kinds of insects, and a few species of lizards. It does not normally occur in mammals because of their imprinted genes. However, using special manipulations to circumvent imprinting, laboratory mice have been produced by parthenogenesis. [Link]
In a few nonmammalian species it is the only method of reproduction, but more commonly animals turn to parthenogenesis only at certain times. For example, aphids use parthenogenesis in the spring when they find themselves with ample food. Reproduction by parthenogenesis is more rapid that sexual reproduction, and the use of this mode of asexual reproduction permits the animals to quickly exploit the available resources.
Parthenogenesis is forced on some species of wasps when they become infected with bacteria (in the genus Wolbachia). Wolbachia can pass to a new generation through eggs, but not through sperm, so it is advantageous to the bacterium for females to be made rather that males.
In these wasps (as in honeybees),
fertilized eggs (diploid) become females;
unfertilized (haploid) eggs become males.
However, in Wolbachia-infected females, all their eggs undergo endoreplication producing diploid eggs that develop into females without fertilization; that is, by parthenogenesis.
Treating the wasps with an antibiotic kills off the bacteria and "cures" the parthenogenesis!
Apis mellifera capensis
Occasionally worker honeybees develop ovaries and lay unfertilized eggs. Usually these are haploid, as you would expect, and develop into males. However, workers of the subspecies Apis mellifera capensis (the Cape honeybee) can lay unfertilized diploid eggs that develop into females (who continue the practice). The eggs are produced by meiosis, but then the polar body nucleus fuses with the egg nucleus restoring diploidy (2n). (The phenomenon is called automictic thelytoky.)
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Here is something I found on parthenogenesis. If I am reading this correctly, there is an outside chance that these corns would be male (haploid) and therefore look different from their mother. Not sure, but it's all I've got. Please post pics ASAP.
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