parthenogenesis

(redirected from Parthenogen)
Also found in: Dictionary, Thesaurus, Encyclopedia.

parthenogenesis

 [pahr″thĕ-no-jen´ĕ-sis]
a modified form of sexual reproduction in which a gamete develops into a new individual without the fertilization of an oocyte by a spermatozoon, as in certain arthropods and other animals; it may occur as a natural phenomenon or be induced by chemical or mechanical stimulation (artificial parthenogenesis). adj., adj parthenogenet´ic.

par·the·no·gen·e·sis

(par'the-nō-jen'ĕ-sis),
A form of nonsexual reproduction, or agamogenesis, in which the female reproduces its kind without fecundation by the male.
[G. parthenos, virgin, + genesis, product]

parthenogenesis

(pär′thə-nō-jĕn′ĭ-sĭs)
n.
1. A form of reproduction in which an unfertilized egg develops into a new individual, occurring commonly among insects and certain other arthropods.
2. The artificial activation of an unfertilized usually mammalian egg, resulting in an embryolike cell cluster from which stem cells can be harvested.

par′the·no·ge·net′ic (-jə-nĕt′ĭk), par′the·no·gen′ic (-jĕn′ĭk) adj.
par′the·no·ge·net′i·cal·ly adv.

par·the·no·gen·e·sis

(pahr'thĕ-nō-jen'ĕ-sis)
A form of nonsexual reproduction, or agamogenesis, in which the female reproduces its kind without fecundation by the male.
[G. parthenos, virgin, + genesis, product]

parthenogenesis

The development of an unfertilized egg into an adult organism. Virgin birth. This occurs naturally in bees and ants and in some animal species development of an ovum can be induced chemically or by pricking with a fine glass fibre. The result is a clone of the mother cell identical in all respects. Only females can be produced by parthenogenesis, as no Y chromosome is present. If achieved, human parthenogenesis would make men biologically redundant. Very early human embryos derived only from ova have been produced experimentally by a parthenogenetic technique using chemicals that changed the concentration of ions in the ova.

parthenogenesis

the development of an individual from an egg without fertilization by a sperm. The process occurs mainly in lower invertebrates, particularly insects. The egg cell can be HAPLOID (1) to produce, for example, male honeybees (drones) or DIPLOID (1) as produced in wingless female aphids which, during the summer months, produce diploid eggs by MITOSIS that develop into female adults, only forming haploid gametes by MEIOSIS in the autumn prior to normal sexual reproduction.
References in periodicals archive ?
laredoensis A, it was the parthenogen's paternal progenitor Cnemidophorus sexlineatus that was the most abundant whiptail lizard at the site (n = 25 + 10 observed); relatively few C.
Therefore, we suggest that the alterations in phenotypic characteristics, ecology, and behavior are more likely in clones of hybrid origin than in non-hybrid parthenogens. If true, this would suggest that maintenance of sex hypotheses - to which the cost of males is essential - are more relevant for non-hybrids than for interspecific hybrids.
The parthenogens have been found together at several sites in Starr, Hidalgo and Webb counties.
The Cnemidophorus laredoensis complex consists of two, independently derived, diploid parthenogens that commonly coexist in sandy, disturbed habitats in the Rio Grande Valley of southern Texas and northern Mexico (Walker 1987a; 1987b; Abuhteba 1990).
Our results show that a hybrid unisexual taxon - which persists as a self-sustaining clonal parthenogen - not only mates with ancestral males but even produces offspring that incorporate or carry the paternal genome.
gularis dominates nondesert habitats (15 visits to nine sites have produced only three LAR-B because of the haphazard approach to urban and suburban development in Mexico, which generates numerous patches and enclaves of disturbed habitat that are favored by parthenogens (Walker, 1987c).
However, yearly bouts of short-term evolution of the type documented here might also be quite prevalent, particularly in cyclical parthenogens that may be exposed to antagonistic forces of selection at different time periods during the clonal phase or in which the disruption of favorable genotypes caused by genetic slippage during recombination may regularly move populations away from a selectively advantageous phenotype.
In all, 42% of the species apparently lack males and are most probably apomictic parthenogens (Tressler 1959), as genetic studies have now confirmed the reliability of breeding system assignments based on gender determinations (Havel et al.
Under the gene-for-gene hypothesis, a priori expectations for the relative performance of parthenogen and sexual thrips on outcrossed host progeny were less clear-cut.
Alterations in sex determination could have dire consequences to populations of cyclic parthenogens such as D.
In some lizards, the remote relationships between species that later hybridized to form parthenogens are reflected in mitochondrial markers of distant past speciation and differentiation that are carried by the parthenogens (Moritz et al.
lugubris (all female parthenogens) often engage in prolonged agonistic encounters while foraging ([ILLUSTRATION FOR FIGURE 12 OMITTED]; Petren et al.