what does polyploidy result in

What is polyploidy and what are its consequences?

Polyploidy, the condition of possessing more than two complete genomes in a cell, has intrigued biologists for almost a century. Polyploidy is found in many plants and some animal species and today we know that polyploidy has had a role in the evolution of all angiosperms.

Does polyploidy result in speciation?

Polyploidy typically results in instant speciation—the new polyploid may be immediately isolated reproductively from its parent or parents; this process greatly increases biodiversity and provides new genetic material for evolution.

Does polyploidy cause mutation?

Polyploidization, the addition of a complete set of chromosomes to the genome, represents one of the most dramatic mutations known to occur.

How does polyploidy result in sterility?

Polyploids are usually infertile with members of their parent species, because diploid x tetraploid crosses produce sterile triploid progeny. If the triploid is viable, it is infertile, due to some chromosomes being inherited twice, others once, leading to a lack of gene dosage balance in the gametes.

How does polyploidy lead to evolution?

Accumulating evidence indicates that polyploidy can increase mutational and environmental robustness, which might increase the potential for specific adaptation in response to changing environmental conditions or reduce the risk of extinction during periods of environmental upheaval.

How does polyploidy lead to genetic variation?

Polyploids have increased heterozygosity, an attribute that may be beneficial (80, 81). Polyploids also harbor higher levels of genetic and genomic diversity than was anticipated, with recurrent formation from genetically divergent diploid parents and possibly genome rearrangements contributing genetic diversity.

What are the disadvantages of polyploidy in plants?

Among the disadvantages that could lead to less vigor and a reduced adaptive capacity in polyploids are the increased number of chromosomes, and the greater complexity of their pairing and segregation interactions that can cause abnormalities (including aneuploidy) during meiosis and mitosis (Comai, 2005).

What are the effects of polyploidy in plants?

Some of the most important consequences of polyploidy for plant breeding are the increment in plant organs ("gigas" effect), buffering of deleterious mutations, increased heterozygosity, and heterosis (hybrid vigor).

Does polyploidy increase gene flow?

Rare yet accumulating evidence in both plants and animals shows that whole genome duplication (WGD, leading to polyploidy) can break down reproductive barriers, facilitating gene flow between otherwise isolated species.

What is polyploidy in biology?

Polyploidy is defined as an increased number of chromosomes seen as an even multiple of the normal chromosome number for a given cell type. From: Nutraceuticals (Second Edition), 2021.

Can polyploidy reproduce?

Key Results The analyses showed that polyploidy is strongly associated with vegetative reproduction, whereas diploids rely more on seed reproduction.

What causes polyploidy in plants?

Polyploidy arises as the result of total nondisjunction of chromosomes during mitosis or meiosis. Polyploidy is common among plants and has been, in fact, a major source of speciation in the angiosperms. Particularly important is allopolyploidy, which involves the doubling of chromosomes in a hybrid plant.

How does speciation happen?

Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics. The demands of a different environment or the characteristics of the members of the new group will differentiate the new species from their ancestors.

What are the two main types of speciation?

Here, we'll explore these modes of speciation: Allopatric (allo = other, patric = place): New species formed from geographically isolated populations. Peripatric (peri = near, patric = place): New species formed from a small population isolated at the edge of a larger population.

Why is polyploidy a prominent form of sympatric speciation in plants?

Polyploidy is the condition of having more than two full sets of chromosomes. Unlike humans and other animals, plants are often tolerant of changes in their number of chromosome sets, and an increase in chromosome sets, a.k.a. ploidy, can be an instant recipe for plant sympatric speciation.

Can polyploidy contribute to the diversification of angiosperms?

Polyploidy has been described both as an evolutionary dead end and as a major engine of diversification for angiosperms. Two recent studies have found that genera with higher proportions of polyploid species are more species rich.

How do autopolyploids affect fertility?

Autopolyploids possess at least three homologous chromosome sets, which can lead to high rates of multivalent pairing during meiosis (particularly in recently formed autopolyploids, also known as neopolyploids) and an associated decrease in fertility due to the production of aneuploid gametes. Natural or artificial selection for fertility can quickly stabilize meiosis in autopolyploids by restoring bivalent pairing during meiosis, but the high degree of homology among duplicated chromosomes causes autopolyploids to display polysomic inheritance. This trait is often used as a diagnostic criterion to distinguish autopolyploids from allopolyploids, which commonly display disomic inheritance after they progress past the neopolyploid stage. While most polyploid species are unambiguously characterized as either autopolyploid or allopolyploid, these categories represent the ends of a spectrum of divergence between parental subgenomes. Polyploids that fall between these two extremes, which are often referred to as segmental allopolyploids, may display intermediate levels of polysomic inheritance that vary by locus.

What is the term for a condition in which cells have more than two paired (homologous) sets?

Polyploidy is a condition in which the cells of an organism have more than two paired ( homologous) sets of chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent. However, some organisms are polyploid, and polyploidy is especially common in plants.

How are polyploids labeled?

Polyploid types are labeled according to the number of chromosome sets in the nucleus. The letter x is used to represent the number of chromosomes in a single set:

What are some examples of polyploidy?

Examples in animals are more common in non-vertebrates such as flatworms, leeches, and brine shrimp. Within vertebrates, examples of stable polyploidy include the salmonids and many cyprinids (i.e. carp ). Some fish have as many as 400 chromosomes. Polyploidy also occurs commonly in amphibians; for example the biomedically-important genus Xenopus contains many different species with as many as 12 sets of chromosomes (dodecaploid). Polyploid lizards are also quite common, but are sterile and must reproduce by parthenogenesis. Polyploid mole salamanders (mostly triploids) are all female and reproduce by kleptogenesis, "stealing" spermatophores from diploid males of related species to trigger egg development but not incorporating the males' DNA into the offspring. While mammalian liver cells are polyploid, rare instances of polyploid mammals are known, but most often result in prenatal death.

What is the most common pathway of artificially induced polyploidy?

This is also the most common pathway of artificially induced polyploidy, where methods such as protoplast fusion or treatment with colchicine, oryzalin or mitotic inhibitors are used to disrupt normal mitotic division, which results in the production of polyploid cells.

Why are polyploid crops preferred?

In some situations, polyploid crops are preferred because they are sterile. For example, many seedless fruit varieties are seedless as a result of polyploidy. Such crops are propagated using asexual techniques, such as grafting .

Why is it so difficult to detect a duplication?

Duplication events that occurred long ago in the history of various evolutionary lineages can be difficult to detect because of subsequent diploidization (such that a polyploid starts to behave cytogenetically as a diploid over time) as mutations and gene translations gradually make one copy of each chromosome unlike the other copy. Over time, it is also common for duplicated copies of genes to accumulate mutations and become inactive pseudogenes.

How does hepatic polyploidy affect the liver?

The liver participates in a wide array of activities related to detoxification, protein synthesis/secretion, metabolism, etc. Since polyploid hepatocytes have an increased complement of DNA compared to diploids, it is conceivable that they have altered gene/protein synthesis, leading to robust cellular function. Similar to observations in plants [ 60 ], hepatic genes could be expressed differentially by diploids, tetraploids, octaploids, etc. The expression of unique subsets of genes would, therefore, endow each ploidy class with specialized functions. To test this idea directly, microarray analysis was performed on equivalent amounts of RNA from FACS-isolated diploid, tetraploid, and octaploid hepatocytes from mice [ 61 ]. Interestingly, the study found very few differences in gene expression among the different ploidy classes. In contrast to differential gene expression, the total amount of gene/protein expression could simply increase with nuclear content. For example, gene expression and functional capacity could be elevated fourfold in octaploid hepatocytes compared to diploids. Additional studies are necessary to determine whether the overall transcriptional or translational output per cell varies between diploid and polyploid hepatocytes.

What is the function of polyploidy in the liver?

In this thinking, polyploidy is associated with increased quiescence and decreased proliferative potential . Thus, polyploidy characterizes the final stage in the life of a hepatocyte. In support of this hypothesis, aging has been associated with shortened telomeres and replicative senescence in human livers [53, 54 ]. Since polyploidy increases with age, it is assumed that polyploid hepatocytes have short telomeres and are replication compromised. The geographical location of hepatocytes within the hepatic lobule has also been used to support the association between polyploidy and terminal differentiation. Numerous publications suggest that diploid hepatocytes are preferentially located in the periportal region and polyploid hepatocytes in the pericentral zone [ 55, 56 ]. Hepatocytes are believed to “mature” as they transition from the periportal to pericentral region of the liver where they are ultimately eliminated [ 57 ]. In contrast, others have suggested that diploid and polyploid hepatocytes are distributed randomly throughout the hepatic lobule [ 29 ]. The most compelling evidence against terminal differentiation, as a defining feature of hepatic polyploidy, is that polyploid hepatocytes are actually highly proliferative. In response to a strong regenerative stimulus such as partial hepatectomy, polyploid hepatocytes proliferate to restore liver mass [ 43, 51 ]. Moreover, polyploid hepatocytes, prospectively isolated by fluorescence-activated cell sorting (FACS) or centrifugal elutriation, proliferated extensively in transplantation experiments and in cell culture [ 51, 58, 59 ]. Cell mixing experiments in which genetically marked octaploid and diploid hepatocytes were cotransplanted in defined ratios into Fumarylacetoacetate hydrolase ( Fah )-deficient mice proved that proliferative capacity is nearly identical between ploidy classes [ 21 ]. Thus, terminal differentiation does not accurately characterize hepatocytes with polyploid nuclear content.

How does polyploidization affect speciation?

Much remains to be learned about the impact of polyploidization on speciation, at both these levels. At the first level, it is clear that polyploids often differ phenotypically from their parent species in ecologically important ways as well as having a degree of chromosome-based reproductive isolation, potentially providing them with an easy route to speciation ( Coyne and Orr, 2004 ). Accumulating data suggest that this route, however, is often not ‘instantaneous.’ Indeed, the prevailing view is that a period of gene flow between diploids and recently formed polyploids assists in polyploid establishment, both by increasing genetic variation in the polyploids and by increasing the number of potential mates for the polyploid individuals. Even in those cases where isolation is strong and rapid, it is unclear whether it is the typically invoked chromosomal incompatibilities or other phenotypic differences that are most responsible for the isolation between the new polyploid and its progenitors.

Why are ferns polyploid?

Polyploidy allows duplicated, extra gene copies to mutate and explore new functions ( Otto and Whitton, 2000; Otto, 2007; Soltis et al., 2003; Soltis and Soltis, 1999, 2000 ). These new functions potentially enable polyploids to acquire new biochemical properties and expand into ecological niches, resulting in increased adaptability. Given these advantages, it is not surprising there are many polyploid ferns. In the Australian fern and lycophyte flora, 38% of all species are polyploids, with polyploids more common in particular families ( Tindale and Roy, 2002 ). These numbers match estimates for ferns and lycophytes in general, such that 31% of species derive from polyploidy ( Wood et al., 2009 ). Interestingly, some ferns do not appear to have undergone polyploidization, with fossil nuclei showing the same genome size as living plants ( Bomfleur et al., 2014 ). As data from the first sequenced fern genomes are assessed ( Sessa et al., 2014 ), and with further studies investigating differing expression of parental genomes in a polyploid ( Sigel et al., 2014 ), it is likely that we will gain even further insights into the role that polyploidization has played in the evolution of ferns.

How does polyploidy contribute to life?

Polyploidy has contributed to the rich diversity of life, with ancient polyploidization events (paleopolyploidization) inferred to have occurred early in the evolution of angiosperms, teleost fishes, vertebrates, and yeast, along with numerous recent events (neopolyploidization) in many groups of plants and in some animals. However, the prevalence of polyploids reflects the combination of two processes: the establishment of new polyploid populations and the diversification of these populations, corresponding to the two main sections of this article. The interaction of these processes can be thought of as a balance, whereby new polyploid individuals are constantly added to populations, due largely to errors in meiosis or fertilization. Many of these ploidy mutants are, however, unfit and fail to leave descendants. Occasionally newly formed polyploids are successful and establish new populations. Once established, many of these new polyploid populations form their own species, but these new species are also generally unfit (at least in plants); only rarely are they able to avoid extinction and themselves speciate. That the ultimate fate of most polyploid individuals and populations is extinction does not preclude the potential for rare advantageous polyploids to have important long-term evolutionary consequences, including establishing major branches of the tree of life (Mayrose et al., 2014; Arrigo and Barker, 2012 ).

What is a polyploid cell?

Polyploid organisms are eukaryotes that have more than two complete sets of chromosomes (one from each parent or ancestor) in somatic and germline cells of animals, fungi, and plants. Polyploidy of individual cells or cell types (endopolyploidy), arising from chromosome replication without cell division, is involved in the normal (e.g., secretory cells) or abnormal (e.g., many cancers) development of organisms. Polyploidy or ‘whole-genome duplication’ is an important feature of genome evolution and speciation, and most lineages of plants and animals include rounds of such duplications in their evolutionary history. Many plant species, in particular, have both ancient whole-genome duplications and more recent polyploidy events in their ancestry. Polyploid individuals are found occasionally in all groups of eukaryotic organisms as a result of incorrect meiosis, fertilization, or cell division, although most spontaneously occurring animal polyploids are inviable. Polyploids can be generated experimentally by treatment with chemicals such as colchicine or by fusion of diploid nuclei. Many polyploids, particularly among plants, develop normally, and depending on the nature of the polyploidy may be sterile, or undergo meiosis that is indistinguishable from a normal diploid giving viable gametes.

How is sexual polyploidization formed?

Sexual polyploidization is the process by which a polyploid zygote is formed by natural fertilization involving 2 n gametes. The case of interploidy crosses (eg, 2 x –4 x or 4 x –2 x ), where one 2 n gamete fertilizes a normally reduced gamete has been termed “unilateral polyploidization,” whereas “bilateral polyploidization” is characterized by the fusion of two 2 n gametes (as might occur in a 2 x –2 x cross). Depending on its origin, a single 2 n gamete may convey little or nearly all of the heterozygosity present in somatic cells. In order to maximize heterozygosity in the polyploid progeny produced by sexual polyploidization, the use of FDR type gametes is preferable to the use of SDR gametes.

Why is polyploidy important?

This is due to increase in number of genes on the chromosomes. Hence, polyploidy is of great importance in the development of taxonomic series.

How is colchicine applied?

It is usually applied in aqueous solution, dilute alcohol, appropriate emulsion, lanoline paste, agar solution, glycerine, cold water. It may be used up in the range of 0.0006% —1% concentration.

What is it called when an organism has more than two sets of homologous chromosomes?

An organism having more than two sets of homologous chromosomes is known as polyploid and the phenomenon polyploidy. It was discovered by Lutz. It is rarely found in animals but is of general occurrence in plants. A survey of the chromosome numbers of the species in a family shows that these species generally fall in to polyploid series e.g., 2n, 3n, 4n, 5n, 6n etc.

What is the name of the hybrid with two A and two B genomes?

The doubling of chromosome in this F 1 hybrid (AB) will give rise to a tetraploid with two A and two B genomes. Such a polyploid is called an allopolyploid or amphidiploid (form derived from a hybrid between two diploids, so that the homologues come from different sources).

How many chromosomes are in Solanaceae?

Thus, the different species of Solanaceae form a polyploid series with a basic chromosome number of 12.

Why are some species grouped together under a taxonomic head?

The species are grouped together under a taxonomic head due to certain morphological similarities and relationships.

What is an autopolyploid?

Autopolyploid are those polyploids, which have the same basic set of chromosomes multiplied. For example, if a diploid species has two similar sets of chromosomes or genomes (AA) an auto-tri-polyploid will have three similar genomes (AAA) and an autotetraploid will have four such genomes (AAAA).

What is polyploidy in plants?

Where as Polyploidy is a condition where there will be addition of two or more set of the chromosomes and this condition mostly occurs only in plants and it is also beneficial among them by providing excess yield than normal and this condition is mostly possible with hybrid plants.

What are the two types of ploidy?

Generally, there are two types of ploidy they are autopolyploidy and allopolyploidy which is also known as amphipolyploidy. These are also subdivided into many categories.

What is the effect of allopolyploidy on the fertility of plants?

This condition often results in bivalents of the species which increases the rate of fertility in offspring. Mostly allopolyploidy causes only reduced vigour in plants.

How many extra chromosomes are in a polyploid cell?

It results in many disorders and abnormalities in functioning of a cell. Where the cell with this polyploid condition has three or more extra chromosomes.

What is polyploidity in biology?

As said earlier polyploid is a condition where an organism have a greater number of chromosomes than normal.

Why is polyploidy important?

Polyploidy is one of the important and major cause the evolution the species. It is very important for the plants in increasing their vigour and size.

Why do polyploid cells form?

Polyploid generally occurs due to an abnormal cell division during the phases of mitosis or meiosis.

What is polyploidy in biology?

Polyploidy is a type of euploidy. In euploidy, any change in the number of chromosomes is the multiple of the number of chromosomes in a basic set or it occurs due to variation in one (haploidy) or more haploid sets of chromosomes (polyploidy).

What is an autopolyploid?

Autopolyploids are polyploids with multiple chromosome sets derived from a single taxon. Most instances of autopolyploidy result from the fusion of unreduced (2n) gametes, which results in either triploid (n + 2n = 3n) or tetraploid (2n + 2n = 4n) offspring

What are polyploids labeled according to?

Polyploid types are labeled according to the number of chromosome sets in the nucleus. haploid, diploid, triploid, tetraploid to

What does "ploidy" mean in biology?

And like that PLOIDY means the number of sets of chromosomes in a cell, or in the cells of an organism.

What is it called when a cell has more than two chromosomes?

Polyploidy is a condition in which the cells of an organism have more than two paired (homologous) sets of chromosomes. Polyploidy is especially common in plants though it is also observed in some animals.

Why are polyploid crops preferred?

In some situations, polyploid crops are preferred because they are sterile. For example, many seedless fruit varieties are seedless as a result of polyploidy. Such crops are propagated using asexual techniques, such as

What is the failure of cytokinesis after telophase?

Failure of cytokinesis after telophase stage of cell division result in an increase whole set of chromosomes in an organisms and , this phenomena is known as polyploidy.

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