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What are polyploids?
What are polyploids?
Organisms with multiple sets of chromosomes in excess of the diploid number.
Based on their chromosomal composition, polyploids are classified into two main categories. What are these categories?
Based on their chromosomal composition, polyploids are classified into two main categories. What are these categories?
Euploids constitute the majority of polyploids.
Euploids constitute the majority of polyploids.
True
Which of the following are examples of naturally occurring autopolyploids?
Which of the following are examples of naturally occurring autopolyploids?
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How do allopolyploids arise?
How do allopolyploids arise?
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Which of these species are examples of commercially important alloploid crops?
Which of these species are examples of commercially important alloploid crops?
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Aneuploids result from the formation of univalents and multivalents during meiosis of euploids.
Aneuploids result from the formation of univalents and multivalents during meiosis of euploids.
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Match the aneuploid term with its corresponding chromosome number.
Match the aneuploid term with its corresponding chromosome number.
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Polyploidization can occur through either natural or artificial methods.
Polyploidization can occur through either natural or artificial methods.
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What is the gigas effect?
What is the gigas effect?
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The increase in cell volume in polyploids is primarily due to increased biomass.
The increase in cell volume in polyploids is primarily due to increased biomass.
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What are chimeras in plants?
What are chimeras in plants?
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What are examples of applications of polyploidy in plant breeding?
What are examples of applications of polyploidy in plant breeding?
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Polyploids can tolerate mutations better than diploids.
Polyploids can tolerate mutations better than diploids.
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What is bridge crossing?
What is bridge crossing?
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What is the main advantage of polyploidy in plant breeding?
What is the main advantage of polyploidy in plant breeding?
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Polyploidy can lead to plants with reduced reproductive success.
Polyploidy can lead to plants with reduced reproductive success.
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Which of these is NOT a typical disadvantage of polyploidy in plant breeding?
Which of these is NOT a typical disadvantage of polyploidy in plant breeding?
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What is the main application of polyploidy in the production of seedless fruits?
What is the main application of polyploidy in the production of seedless fruits?
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Polyploidy can be used in the production of fruits with altered shapes and sizes.
Polyploidy can be used in the production of fruits with altered shapes and sizes.
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Aneuploidy can be used to overcome sterility in plants.
Aneuploidy can be used to overcome sterility in plants.
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What are the benefits of using polyploidy in ornamental and forage breeding?
What are the benefits of using polyploidy in ornamental and forage breeding?
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Polyploidy is widely used in breeding crops for increased disease resistance.
Polyploidy is widely used in breeding crops for increased disease resistance.
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Polyploidy can increase a plant's tolerance to stress factors such as drought and high temperatures.
Polyploidy can increase a plant's tolerance to stress factors such as drought and high temperatures.
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Polyploidy is a tool for increasing crop yields.
Polyploidy is a tool for increasing crop yields.
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The use of pesticides and herbicides can lead to the unintended creation of polyploids in plants.
The use of pesticides and herbicides can lead to the unintended creation of polyploids in plants.
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Polyploidy is often a sign of a plant's vulnerability to diseases and pests.
Polyploidy is often a sign of a plant's vulnerability to diseases and pests.
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Polyploidy is only found in plants, not in animals.
Polyploidy is only found in plants, not in animals.
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Study Notes
Polyploids in Plants
- Polyploids are organisms possessing multiple sets of chromosomes exceeding the diploid number.
- Polyploidy is widespread in nature, crucial for adaptation and speciation.
- Approximately 50-70% of angiosperms, encompassing numerous crops, have experienced polyploidy during their evolutionary journey.
Classification of Polyploids
- Polyploids are categorized based on their chromosomal composition into euploids and aneuploids.
- Euploids, comprising the majority, have complete multiple sets of chromosomes specific to a species.
- Euploids are further classified into autopolyploids and allopolyploids based on genome composition.
Autopolyploidy
- Autopolyploidy involves the presence of multiple copies of the same basic set of chromosomes within a species.
- This arises from the failure of chromosomes to separate during meiosis, resulting in unreduced gametes.
- Natural examples include tetraploid alfalfa, peanuts, potatoes, coffee, and triploid bananas.
Allopolyploidy
- Allopolyploidy results from the combination of genomes from distinct species.
- This typically involves hybridization followed by chromosome doubling.
- Economically significant allopolyploid crops include strawberries, wheat, oats, upland cotton, oilseed rape, blueberries, and mustard.
Aneuploidy
- Aneuploids differ from euploids by possessing additions or subtractions of one or more specific chromosomes.
- Aneuploids originate from meiotic errors, such as non-disjunction, leading to an uneven distribution of chromosomes.
- Different categories of aneuploids include monosomy (2n-1), nullisomy (2n-2), trisomy (2n+1), tetrasomy (2n+2), and pentasomy (2n+3).
Applications of Polyploids
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Mutation Breeding: Polyploids tolerate deleterious allele modifications post-mutation and possess higher mutation frequency due to duplicated genes. This higher frequency can be utilized to induce mutations in diploid cultivars that do not generate enough genetic variation after treatment with mutagens.
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Seedless Fruits: Polyploids, such as induced autotetraploids in watermelons, are used to produce seedless triploid hybrids.
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Bridge Crossing: This method utilizes the reproductive superiority of polyploids to overcome sexual incompatibility issues between two species by creating fertile hybrid bridge species.
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Ornamental and Forage Breeding: Polyploidy results in larger plant organs, termed the "giga effect," owing primarily to increased water content. While this provides enlarged seeds and elevated seed protein contents, it is often offset by lower seed set. Enhanced qualities in blossoms and flower periods make polyploids valuable in ornamental breeding.
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Disease Resistance: Aneuploidy, used in breeding strategies for disease-resistant crops (e.g., leaf rust resistance in wheat). This might entail chromosome deletion, substitution, or the presence of supernumerary chromosomes.
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Industrial Applications: Polyploids, like tetraploid Dioscorea zingiberensis, enhance the production of secondary metabolites (e.g., alkaloids and terpenes), boosting the synthesis of sex hormones and corticosteroids. This also offers resistance to pests and pathogens.
Advantages of Polyploids
- Enlarged Size and Increased Vigor: Polyploids often display enhanced vigor, an advantage exploited in breeding.
- Restoration of Fertility: Polyploids can restore fertility in species that exhibit infertility during hybridization.
- Overcoming Hybridization Barriers: They can bridge the reproductive gap found between incompatible species.
- Pest and Stress Tolerance: Some polyploids exhibit improved tolerance to pest or stress.
- Creation of Sterile Triploids: Polyploids are vital for generating sterile hybrid triploid species.
Disadvantages of Polyploids
- Inbreeding Problems: Inbreeding can result in various issues with polyploid crops.
- Sterility Issues: Polyploidy can negatively impact sterility rates or lead to infertility to varying degrees.
- Inheritance Problems: Polyploidy has implications on the patterns of inheritance, impacting their use in population genetics work.
Chimeras
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Plants or parts of a plant that are composed of genetically distinct cell layers.
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Mericlinal: A mutation occurs in one layer causing changes along the side of the apex.
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Periclinal: A mutation occurs within a layer at the top of the plant's apical region affecting the whole layer and is stable.
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Sectorial: Mutations occur in multiple layers. The area affected is stable.
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Description
This quiz explores the concept of polyploidy in plants, including its classification and significance in evolution. Learn about euploids and aneuploids, as well as the processes of autopolyploidy and allopolyploidy. Dive into the role polyploids play in the adaptation and speciation of angiosperms.
