Main Difference – Autopolyploidy vs Allopolyploidy
Autopolyploidy and allopolyploidy are two types of anomaly that lead to polyploidy. Polyploidy often occurs due to the nondisjunction of chromosomes during the cell division. The nondisjunction is the improper split of sister chromatids or homologous chromosomes, which may occur during the nuclear division. It can occur naturally or under the influence of chemicals. The main difference between autopolyploidy and allopolyploidy is that autopolyploidy is the containment of multiple sets of chromosomes that are derived from the same species whereas allopolyploidy is the containment of multiple sets of chromosomes that are derived from different species.
Key Areas Covered
1. What is Autopolyploidy
– Definition, Characteristics, Function
2. What is Allopolyploidy
– Definition, Characteristics, Function
3. What are the Similarities Between Autopolyploidy and Allopolyploidy
– Outline of Common Features
4. What is the Difference Between Autopolyploidy and Allopolyploidy
– Comparison of Key Differences
Key Terms: Allopolyploidy, Autopolyploidy, Hybrid Species, Meiosis, Mitosis, Nondisjunction of Chromosomes, Polyploidy, Sympatric Speciation
What is Autopolyploidy
Autopolyploidy refers to a type of polyploidy in which the chromosome complement consists of more than two copies of homologous chromosomes. It occurs by the fusion of gametes of the same parent. Typically, most eukaryotic organisms are diploid in their lifetime. This means they possess two sets of chromosomes. Autopolyploidy arises by the doubling of the chromosome number of the diploid species. Autopolyploidy can possess either three (triploid), four (tetrapolyploid), five (pentapolyploid), six (hexapolyploid) or more copies of the same genome.
Figure 1: Autopolyploidy
Autopolyploidy can occur in two ways: nondisjunction of gametes and genome duplication. The nondisjunction of chromosomes can occur in both mitosis and meiosis. The mitotic nondisjunction may occur in the early embryo, forming polyploid new individuals. In the meiosis, the fusion of a haploid gamete with a diploid gamete may also produce a triploid zygote. All chromosome sets in an autopolyploid individual are homologous to each other. Because of this, the aligning of the homologous chromosomes at the prophase 1 of meiosis 1 is difficult. As an example, in triploidy, three homologous chromosomes occur in the cell, and only two can pair during cell division. The third chromosome segregates randomly. Therefore, the resulting gametes may contain unbalanced chromosome numbers of different chromosomes. This may produce an unbalanced number of chromosomes in the zygote. The unbalanced gene dosage may be lethal. Autopolyploidy may occur by genome duplication as well. The genome duplication can occur by meiotic non-reduction of the gametes. The formation of the tetraploid zygote by the fusion of two diploid gametes is shown in figure 1.
What is Allopolyploidy
Allopolyploidy refers to a type of polyploidy in which the chromosome complement consists of more than two copies of chromosomes derived from different species. It occurs when two species mate to produce a hybrid species. The mule which is produced by the mating of a male donkey with a female horse is an example of a hybrid. The mating of two different species may produce a sympatric species, which is infertile with both parental species due to the allopolyploidy.
Figure 2: Wheat
Sympatric speciation commonly occurs in wheat, which is a type of grass. The wheat pollen can fuse with other species in the same genus, producing sympatric species. Wheat is a combination of three types of grasses. The meiosis occurs perfectly in these types of sympatric species since each type of chromosome set consists of another homologous chromosome set to pair.
Similarities Between Autopolyploidy and Allopolyploidy
- Autopolyploidy and allopolyploidy are two types of cell division anomalies.
- Both autopolyploidy and allopolyploidy occur by the nondisjunction of sister chromatids or chromosomes during prophase 1 and prophase 2 respectively.
- Both autopolyploidy and allopolyploidy lead to polyploidy where multiple sets of chromosomes occur in the nucleus.
- Both autopolyploidy and allopolyploidy mostly occur in plants.
- Both autopolyploidy and allopolyploidy can occur naturally or under the influence of chemicals such as colchicine.
Difference Between Autopolyploidy and Allopolyploidy
Definition
Autopolyploidy: Autopolyploidy refers to a type of polyploidy where the chromosome complement consists of more than two copies of homologous chromosomes.
Allopolyploidy: Allopolyploidy refers to a type of polyploidy where the chromosome complement consists of more than two copies of chromosomes derived from different species.
Arise
Autopolyploidy: Autopolyploidy arises by the fusion of gametes of the same species.
Allopolyploidy: Allopolyploidy arises by the fusion of gametes of the different species.
Consist of
Autopolyploidy: An autopolyploid cell contains homologous chromosome sets.
Allopolyploidy: All chromosome sets of an allopolyploid cell are not homologous.
Cause
Autopolyploidy: Autopolyploidy is mainly caused by nondisjunction of chromosomes.
Allopolyploidy: Allopolyploidy is caused by mating of different species.
Meiosis
Autopolyploidy: An autopolyploid cell does not undergo meiosis since it has arisen from one parent.
Allopolyploidy: An allopolyploid cell can undergo meiosis.
Examples
Autopolyploidy: Autopolyploidy is seen in crops such as wheat, oats, sugar-cane, potato, peanut, banana, and coffee.
Allopolyploidy: Allopolyploidy is seen in crops such as wheat and animals such as mules.
Conclusion
Autopolyploidy and allopolyploidy are two types of cell division anomalies, which lead to polyploidy. Autopolyploidy is the containment of multiple copies of chromosomes in the same parent. Allopolyploidy is the containment of the multiple copies of chromosomes of different species. Autopolyploidy mainly occurs due to nondisjunction of chromosomes. Allopolyploidy occurs by the mating of different species. The main difference between autopolyploidy and allopolyploidy is the type of chromosome sets in their nucleus.
Reference:
1.“ Autopolyploidy.” LinkedIn SlideShare, 16 Dec. 2015, Available here. Accessed 29 Sept. 2017.
2.“Allopolyploidy.” BioNinja, Available here. Accessed 29 Sept. 2017.
Image Courtesy:
1. “Polyploidization” (Public Domain) via Commons Wikimedia
2. “Wheat close-up” By User:Bluemoose – Own work (CC BY-SA 3.0) via Commons Wikimedia
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