How Does Polyploidy Influence Evolution and Crop Improvement?
Polyploid means a condition where an organism acquires or general diploid cell involved into one or a set of chromosomes. Sometimes it involves more than one set of chromosomes. In Polyploidy it has been found that it is one of the heritable conditions and more than two sets of chromosomes possess into that process. It has been found that Polyploidies are primarily standard in plants. It has also been found that significant angiosperms and speciation are the multiple sources of polyploidy.
Polyploidy plays a vital role in the process of doubling the chromosomes in hybrid plants. It is essential for allopolyploid. Not only in the plants' polyploidy is also found in certain groups of amphibians and fish. For example, some salamanders, leeches, and frogs belong to this. The Polyploid Organism or cell has three haploid chromosome numbers; sometimes more than three also can be seen. During meiosis, it has been found that it does not need the homologous pairs for gamete's successful formation; hybrid is generally sterile. The plants inherit from each parent and they duplicate the set of chromosomes; meiosis can happen at this stage. As every chromosome has a duplicate set that is derived by homologue.
In this way, Polyploidies provide fertility on the previously sterile hybrid and achieves a different form of species than the parents. Half of the angiosperm comes through polyploidy. Some of the species are important for humans. Polyploidy in humans is rarely observed. The presence of polyploid cells is seen in differentiated tissues such as the placenta, heart muscles, bone marrow, and liver parenchyma By using this plant's breeding methods, it has been found that polyploidy is used for treating hybrids. It has been observed that polyploidy is rare in animals, and it can be seen primarily on plants.
Polyploidy in Plants
It has been found that polyploidy exists in the cells; polyploidy found in more than two cells in the chromosome. Polyploidy can be the outcome of random multiplication of one plant through hybridization or genetic material. Polyploidy is hugely found in domesticated crops. Polyploidy is the outcome of chromosome non-disjunction during meiosis or mitosis. Polyploidy mostly can be seen in plants, and it mostly finds in the angiosperms. Polyploidy involves the process of doubling the chromosomes in hybrid plants. At the time of evaluation, polyploidy Polyploidy plays a significant role in the cultivated plants and wild plants. The most stimulating effects of polyploidy are that it is used to plant plants, and it helps plants gain excess plant organs. Polyploid plays a crucial function in the breeding process of plants and crop improvement.
Types of Polyploidy
Polyploidy refers to such a condition where more than two pairs of chromosomes have been found in a creature's cells. It has been found that there are variations of Polyploid that existed in the living being, and according to that, a difference has been found. Tetraploids are one of the variations of polyploids where the chromosomes consist of four sets. Chromosomes consist of six groups known as Hexaploids. Allopolyploidy, Autopolyploidy, and Auto-Allopolyploid are the three types of polyploidy. It has been found that due to polyploidy, different variation chromosomes can be seen.
Aneuploidy and Polyploidy
Aneuploidy refers to a state of the chromosomes where extra chromosomes and missing chromosomes have been found in the cell. It has been found that when women conceive at a higher age, the chances of Aneuploidy are increased. Aneuploidy can be found due to missing chromosomes or unbalanced chromosome sets. It has been found that the absence of more than one set of chromosomes can be the reason for Aneuploid. More than two sets of chromosomes are one of the reasons for polyploidy. Polyploidy can be seen primarily on plants, and Aneuploidy has been primarily found in humans. A fresh set of the chromosome is created by polyploidy, wherein a haploid abnormality of chromosomes is found for the Aneuploidy.
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Polyploidy Breeding
Polyploidy breeding has been primarily found in the plants, and it has been found that Polyploid Plants have the adapting capability. The particular effect of polyploidy is it affects species-to-species. On evaluating plants, polyploidy has played a significant part; by the polyploidy breeding, a completely different form of species can be formed that does not bear the identity of both of the parent plants.
Polyploidy in Crop Improvement
Polyploidy plays a vital role in the evaluation and crop development. Many crops have been found that are domesticated by the nature of polyploidy. Wheat is considered the world's most staple food. This is a variation of grass and is cultivated widely for the making of cereal food. One of the greatest examples of polyploidy is wheat, and it grows naturally. Sometimes polyploidy is induced artificially, mainly by the Antimitotic agents, which help plants for breeding. Polyploidy duplicates the entire set of chromosomes and forms a new variation. One of the critical impacts of polyploidy is it helps increase the size of the cells and happens due to the extra gene copies. Polyploidy is used for changing the colour of the flour, the size, and the shape of the flower. With the help of polyploidy, diversification of crops can be found.
FAQs on Polyploidy in Biology: Meaning, Types & Importance
1. What is polyploidy and what are some common examples from the NCERT syllabus?
Polyploidy is a genetic condition where an organism has more than two complete sets of chromosomes. Normal diploid organisms have two sets (2n), while polyploids can have three (triploid, 3n), four (tetraploid, 4n), or more sets. This phenomenon is particularly common in plants. Well-known examples include Triticale (a hybrid of wheat and rye), common bread wheat (hexaploid, 6n), and many cultivated fruits like strawberries (octoploid, 8n) and bananas (triploid, 3n).
2. What are the main types of polyploidy?
Polyploidy is primarily classified into two main types based on the origin of the chromosome sets:
- Autopolyploidy: This occurs when an individual has more than two chromosome sets that are all derived from a single species. It can result from the non-disjunction of all chromosomes during mitosis or meiosis, leading to, for example, a tetraploid (4n) from a diploid (2n) parent.
- Allopolyploidy: This occurs when an individual has chromosome sets derived from two or more different species. It typically involves the hybridisation of two species followed by chromosome doubling, creating a fertile hybrid that is reproductively isolated from its parent species.
3. How does polyploidy differ from aneuploidy?
The key difference lies in what part of the chromosome set is affected. Polyploidy involves the gain of one or more entire sets of chromosomes (e.g., 3n, 4n, 6n). In contrast, aneuploidy is the gain or loss of one or more individual chromosomes, leading to an abnormal number that is not a multiple of the haploid set (e.g., 2n+1 or 2n-1). Disorders like Down's Syndrome (Trisomy 21) are examples of aneuploidy, not polyploidy.
4. Why are many polyploid plants viable and successful, while polyploidy is generally lethal in humans?
Polyploidy is tolerated in plants because their development is more flexible and less dependent on a strict gene dosage balance. In fact, the extra genetic material can lead to advantageous traits like larger organs (fruits, flowers). In humans and most animals, development relies on a very precise balance of proteins produced by genes across all chromosomes. A massive change like an entire extra set of chromosomes (e.g., triploidy) disrupts this delicate balance so severely that it leads to catastrophic developmental failures, typically resulting in miscarriage.
5. What is the significance of polyploidy in agriculture and plant evolution?
Polyploidy is highly significant in both fields. In agriculture, it is a major tool for crop improvement, often resulting in plants with larger fruits, seeds, and leaves, or creating seedless varieties like watermelon (triploid). In plant evolution, polyploidy is a primary mechanism for sympatric speciation, where new species arise in the same geographic area. It creates instant reproductive isolation, allowing a new polyploid plant line to evolve independently from its diploid ancestors.
6. How can polyploidy be artificially induced in plants?
Polyploidy can be artificially induced in plants, most commonly by using the chemical colchicine. This alkaloid is applied to a plant's growing tips or seeds. Colchicine works by disrupting the formation of spindle fibres during mitosis. As a result, chromosomes replicate, but the cell does not divide, leading to a doubling of the chromosome number within the cell. This technique is widely used in horticulture and agriculture to create new plant varieties with desirable traits.
7. Why are organisms with an odd number of chromosome sets, like triploids (3n), usually sterile?
Sterility in organisms with an odd number of chromosome sets is caused by problems during meiosis. For gametes to be viable, they must receive a complete, balanced set of chromosomes. In a triploid (3n) organism, the three homologous chromosomes cannot pair up evenly during Meiosis I. This leads to an unequal separation of chromosomes into the resulting gametes. Most gametes end up with an incomplete or imbalanced number of chromosomes (aneuploid), rendering them non-functional and causing the organism to be sterile.
