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Questions and Answers
What is euploidy commonly referred to as?
What is euploidy commonly referred to as?
Which of the following is NOT a type of aneuploidy?
Which of the following is NOT a type of aneuploidy?
What is a characteristic of polyploids compared to diploids?
What is a characteristic of polyploids compared to diploids?
How are polyploids commonly induced in the laboratory?
How are polyploids commonly induced in the laboratory?
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Which plant species was the first to report polyploidy?
Which plant species was the first to report polyploidy?
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What effect does colchicine have on mitosis?
What effect does colchicine have on mitosis?
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What is the main requirement for an organism to be classified as a polypoid?
What is the main requirement for an organism to be classified as a polypoid?
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Which of the following best describes an autopolyploid?
Which of the following best describes an autopolyploid?
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Which of the following is a consequence of polyploidy in plants?
Which of the following is a consequence of polyploidy in plants?
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Which type of aneuploidy results in a cell with one fewer chromosome than normal?
Which type of aneuploidy results in a cell with one fewer chromosome than normal?
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Which of the following is an example of an allopolyploid?
Which of the following is an example of an allopolyploid?
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What is one of the applications of autopolyploidy in crop improvement?
What is one of the applications of autopolyploidy in crop improvement?
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Which triploid crops are noted for being sterile and seedless?
Which triploid crops are noted for being sterile and seedless?
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Autotetraploids are generally considered more successful because of their:
Autotetraploids are generally considered more successful because of their:
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In the context of polyploidy, what is a characteristic of triploids?
In the context of polyploidy, what is a characteristic of triploids?
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Which of the following crops is a known example of an autopolyploid?
Which of the following crops is a known example of an autopolyploid?
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What is the primary benefit of creating Triticale?
What is the primary benefit of creating Triticale?
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From which two parent species is Raphanobrassica synthesized?
From which two parent species is Raphanobrassica synthesized?
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What distinguishes allopolyploidy in crop species creation?
What distinguishes allopolyploidy in crop species creation?
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What is the ploidy level of Triticum dicoccum?
What is the ploidy level of Triticum dicoccum?
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Which feature of Triticale makes it suitable for adverse environments?
Which feature of Triticale makes it suitable for adverse environments?
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What is the resulting ploidy level after spontaneous chromosome doubling of ABD?
What is the resulting ploidy level after spontaneous chromosome doubling of ABD?
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What is a key characteristic of Raphanobrassica?
What is a key characteristic of Raphanobrassica?
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What does the abbreviation 'n' represent in the context of chromosome numbers?
What does the abbreviation 'n' represent in the context of chromosome numbers?
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What is the primary reason for the greater success of allopolyploids compared to autopolyploids in crop species?
What is the primary reason for the greater success of allopolyploids compared to autopolyploids in crop species?
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What is required in the production of allopolyploids after creating F1 hybrids?
What is required in the production of allopolyploids after creating F1 hybrids?
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Which of the following describes allopolyploidy?
Which of the following describes allopolyploidy?
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Which hybrid contributed to the creation of the allotetraploid Raphanobrassica?
Which hybrid contributed to the creation of the allotetraploid Raphanobrassica?
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What are synthetic allopolyploids?
What are synthetic allopolyploids?
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What role does colchicine play in the production of allopolyploids?
What role does colchicine play in the production of allopolyploids?
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Which species is NOT considered a contributing genome source for Triticum aestivum?
Which species is NOT considered a contributing genome source for Triticum aestivum?
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In addition to bread wheat, which other crop species has benefited from allopolyploidy?
In addition to bread wheat, which other crop species has benefited from allopolyploidy?
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Study Notes
Polyploidy in Plants
- Polyploidy is the presence of more than two sets of chromosomes in a cell.
- Polyploidy is common in plants and is estimated to occur in about one-third of angiosperms.
- Euploidy is a type of polyploidy involving the gain or loss of an entire set of chromosomes.
- Aneuploidy is the presence of an abnormal number of chromosomes in a cell, involving the gain or loss of one or a few chromosomes.
- Types of aneuploidy are monosomy (2n-1), trisomy (2n+1) and nullisomy (2n-2).
Characteristics of Polyploids
- Polyploids generally have larger cells than diploid plants.
- Polyploid plants often have larger and thicker leaves, larger flowers and fruits.
- They may exhibit increased vigor and vegetative growth.
Origin of Polyploids
- Polyploids may arise spontaneously.
- Polyploids may be induced through physical or chemical agents such as heat, cold treatment, or chemicals like colchicine.
Colchicine
- Colchicine is a poisonous chemical isolated from the seeds and bulbs of the autumn crocus (Colchicum autumnale).
- Colchicine inhibits spindle formation, preventing the separation of sister chromatids during cell division.
- This results in chromosome doubling as the nucleus includes all of the chromatids.
Types of Polyploids
- Polyploids are categorized into two main types: autopolyploids and allopolyploids.
- Autopolyploids have identical sets of genomes (e.g., AAAA), derived from a single species.
- Allopolyploids have genomes from two or more distinct species (e.g., AABB).
Autopolyploidy Examples
- Seedless triploid watermelons, tomatoes, and grapes are examples of autopolyploids.
- Potato is an autotetraploid (4x).
- Coffee is an autotetraploid (4x).
- Banana is an autotriploid (3x), which is sterile and seedless.
- Sweet potato is an autohexaploid (6x).
Applications of Autopolyploidy in Crop Improvement
- Producing homozygous diploid lines from monoploids (haploids): Chromosome doubling in monoploids can accelerate the process of isolating inbreds and purelines.
- Producing seedless fruits: Triploids, created via hybridization between tetraploids and diploids, are often highly sterile, making them suitable for seedless fruit production.
- Increasing crop vigor and size: Autotetraploids are often larger and more vigorous than their diploid counterparts.
- Improved drought tolerance: A triploid clone of tea (Camellia assamica) has been released for cultivation in the northern parts of India, demonstrating its drought resistance.
Allopolyploidy
- In allopolyploidy, different species contribute genomes to the polyploid offspring.
- Allopolyploids can arise from chromosome doubling in F1 hybrids between two distinct species of the same genus or different genera.
- Synthetic allopolyploids are human-made allopolyploids.
Production of Allopolyploids
- The production of allopolyploids typically involves two steps:
- Production of F1 distant hybrid: Cross-breeding two distinct species.
- Chromosome doubling with the help of colchicine: Doubling the chromosome number of the F1 hybrid to produce an allopolyploid.
Allopolyploid Examples
- Triticale is a synthetic allopolyploid produced by crossing wheat and rye.
- Raphanobrassica is a synthetic allopolyploid produced by crossing cabbage and radish.
Role of Allopolyploidy In Crop Improvement
- Allopolyploids have proven to be more successful as crop species than autopolyploids.
- Many modern crop species are allopolyploids.
The Evolution of Bread Wheat
- Allopolyploidy played a crucial role in the evolution of bread wheat (Triticum aestivum).
- Bread wheat is a hexaploid (6x), containing three different genomes: A, B, and D.
- The A genome is believed to have originated from Triticum monococcum.
- The B genome is believed to have originated from Aegilops speltoides.
- The D genome is believed to have originated from Aegilops squarrosa.
Applications of Allopolyploidy
- Triticale is a synthetic allopolyploid that combines the yielding ability and grain quality of wheat with rye's hardiness to adverse environments.
- Raphanobrassica was an attempt to combine the root of radish with the leaves of cabbage but ultimately resulted in a plant with raddish-like leaves and cabbage-like roots.
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Description
This quiz covers the concept of polyploidy in plants, focusing on its definition, types, characteristics, and origin. You will learn about euploidy and aneuploidy, as well as the effects of polyploidy on plant size and vigor. Test your understanding of how polyploids arise and the role of agents like colchicine.
