These parent-of-origin effects reflect the effects of genomic imprinting.Complete tetraploidy is more rarely diagnosed than triploidy, but is observed in 1–2% of early miscarriages. However, some tetraploid cells are commonly found in chromosome analysis at prenatal diagnosis and these are generally considered harmless. It is not clear whether these tetraploid cells simply tend to arise during in vitro cell culture or whether they are also present in placental cells in vivo. There are, at any rate, very few clinical reports of fetuses/infants diagnosed with tetraploidy mosaicism. Mixoploidy is quite commonly observed in human preimplantation embryos and includes haploid/diploid as well as diploid/tetraploid mixed cell populations. It is unknown whether these embryos fail to implant and are therefore rarely detected in ongoing pregnancies or if there is simply a selective process favoring the diploid cells. Fish
A polyploidy event occurred within the stem lineage of the teleost fish. Plants
Polyploidy is frequent in plants, some estimates suggesting that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes. Huge explosions in angiosperm species diversity appear to have coincided with the timing of ancient genome duplications shared by many species. It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.Polyploid plants can arise spontaneously in nature by several mechanisms, including meiotic or mitotic failures, and fusion of unreduced (2n) gametes. Both autopolyploids (e.g. potato) and allopolyploids (such as canola, wheat and cotton) can be found among both wild and domesticated plant species.
The mechanism by which the genome is accurately restored involves RecA-mediated homologous recombination and a process referred to as extended synthesis-dependent strand annealing (SDSA).Azotobacter vinelandii can contain up to 80 chromosome copies per cell. However this is only observed in fast growing cultures, whereas cultures grown in synthetic minimal media are not polyploid. Archaea
The archaeon Halobacterium salinarium is polyploid and, like Deinococcus radiodurans, is highly resistant to X-ray irradiation and desiccation, conditions that induce DNA double-strand breaks. Although chromosomes are shattered into many fragments, complete chromosomes can be regenerated by making use of overlapping fragments. The mechanism employs single-stranded DNA binding protein and is likely homologous recombinational repair. See also
Diploidization
Eukaryote hybrid genome
Ploidy
Polyploid complex
Polysomy
Reciprocal silencing
Sympatry

References
Further reading
External links

Polyploidy on Kimballs Biology Pages
The polyploidy portal a community-editable project with information, research, education, and a bibliography about polyploidy.