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Polygenic Systems and Inheritance of Quantitative Traits

Most traits important in farm animals are quantitative and have specific characteristics:

  • They are influenced by numerous genes, each with minor individual effects. Identifying individual gene impacts on quantitative traits is typically unfeasible.
  • Various gene actions like additive, dominance, and epistatic effects play a role, with their significance varying across traits.
  • Genetic expression is significantly influenced by the environment, leading to traits with a continuous distribution lacking distinct boundaries between 'good' and 'bad'.

Economic Traits in Livestock

  • Economic traits in livestock refer to characteristics that hold a monetary value in livestock production.

Qualitative Traits:

  • Qualitative traits exhibit distinct differences between phenotypes, such as the clear contrast between black and red colors in Angus cattle.
  • These traits are determined by a pair of genes.

Quantitative Traits:

  • Quantitative traits show a continuous range of phenotypes without sharp distinctions and are influenced by multiple gene pairs.
  • Examples of quantitative traits include gestation length, birth weight, weaning weight, feed efficiency, carcass quality, milk production, and egg production.
  • Environmental conditions significantly impact most quantitative traits, unlike qualitative traits.

Question for Polygenic Systems and Inheritance of Quantitative Traits
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Which of the following statements best describes quantitative traits?
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Quantitative Inheritance in Farm Animals

  • Quantitative inheritance involves complex genetic interactions and environmental influences in traits like backfat thickness in swine.

Genetic Interactions:

  • Multiple gene pairs, both additive and non-additive in nature, can contribute to quantitative traits.
  • Each gene may not have an equal effect on the trait's expression.

Environmental Influence:

  • Environment plays a crucial role in the expression of quantitative traits, alongside genetic factors.
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Genetic Variation:

  • Offspring exhibit a range of backfat thickness due to genetic diversity, with variations from the parental mean.
  • Environmental factors, sex, diet, and other variables contribute to trait expression and variation.
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Gene Action and Environment:

  • Evidence suggests that gene interactions beyond simple additive effects play a significant role in quantitative trait inheritance.
  • Understanding the balance between genetic interactions and environmental influences is key to improving livestock traits through selective breeding.

Question for Polygenic Systems and Inheritance of Quantitative Traits
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What factors contribute to the variation in backfat thickness in farm animals?
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The document Polygenic Systems and Inheritance of Quantitative Traits | Animal Husbandry & Veterinary Science Optional for UPSC is a part of the UPSC Course Animal Husbandry & Veterinary Science Optional for UPSC.
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FAQs on Polygenic Systems and Inheritance of Quantitative Traits - Animal Husbandry & Veterinary Science Optional for UPSC

1. What are polygenic systems and how do they influence the inheritance of quantitative traits in farm animals?
Ans. Polygenic systems refer to traits that are controlled by multiple genes, each making a small contribution to the overall phenotype. Inheritance of quantitative traits in farm animals is complex, as these traits are influenced by both genetic and environmental factors. Polygenic systems result in a continuous variation of traits within a population.
2. What are some examples of economic traits in livestock that are influenced by polygenic inheritance?
Ans. Economic traits in livestock that are influenced by polygenic inheritance include milk production in dairy cows, growth rate in beef cattle, wool yield in sheep, and egg production in poultry. These traits are important for the profitability and productivity of livestock farming operations.
3. How do breeders use knowledge of polygenic inheritance to improve the breeding of farm animals for desirable traits?
Ans. Breeders use knowledge of polygenic inheritance to select animals with desirable traits for breeding purposes. By analyzing the genetic makeup of individuals and their relatives, breeders can identify superior genetic combinations that are likely to produce offspring with improved performance for economic traits.
4. What is the significance of understanding polygenic systems in the context of sustainable livestock production?
Ans. Understanding polygenic systems is important for sustainable livestock production as it allows breeders to make informed decisions to improve animal health, welfare, and productivity. By selecting for traits that are controlled by multiple genes, breeders can enhance the overall performance of livestock populations over time.
5. How can genetic technologies and genomic tools be used to study polygenic inheritance in farm animals?
Ans. Genetic technologies such as genome-wide association studies (GWAS) and genomic selection can be used to study polygenic inheritance in farm animals. These tools allow researchers to identify specific genes and genetic markers that are associated with quantitative traits, providing valuable insights into the genetic basis of complex traits in livestock.

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