Allogamy or cross-fertilization is the

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

of an ovum from one individual with the

spermatozoa A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromos ...

of another. By contrast,

autogamy Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species o ...

is the term used for self-fertilization. In humans, the fertilization event is an instance of allogamy. Self-fertilization occurs in

hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have s ...

organisms where the two

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s fused in fertilization come from the same individual. This is common in

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

s (see

Sexual reproduction in plants Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from eithe ...

) and certain protozoans. In plants, allogamy is used specifically to mean the use of pollen from one plant to fertilize the

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

of another plant and usually synonymous with the term "cross-fertilization" or "cross-pollination" (

outcrossing Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity. Outcrossing can be a usefu ...

). The latter term can be used more specifically to mean pollen exchange between different plant strains or even different plant species (where the term ''cross-hybridization'' can be used) rather than simply between different individuals.

Parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s having complex life cycles can pass through alternate stages of allogamous and autogamous reproduction, and the description of a hitherto unknown allogamous stage can be a significant finding with implications for human disease.

Avoidance of inbreeding depression

Allogamy ordinarily involves cross-fertilization between unrelated individuals leading to the masking of deleterious recessive

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

s in progeny. By contrast, close inbreeding, including self-fertilization in plants and automictic parthenogenesis in hymenoptera, tends to lead to the harmful expression of deleterious recessive alleles (

inbreeding depression Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...

). In dioecious plants, the stigma may receive pollen from several different potential donors. As multiple pollen tubes from the different donors grow through the stigma to reach the ovary, the receiving maternal plant may carry out pollen selection favoring pollen from less related donor plants. Thus post-pollination selection may occur in order to promote allogamy and avoid inbreeding depression. Also, seeds may be aborted selectively depending on donor–recipient relatedness.

References

Reproduction {{biology-stub

Avoidance of inbreeding depression

See also

References