Selective breeding practice, benefits and problems
Inheritance, variation and evolution • Variation and evolution
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Key concepts
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Definition and basic principle
Selective breeding (artificial selection) involves choosing individuals that show a desired variation and breeding them so that offspring inherit those traits. Repeated selection over many generations concentrates alleles for the chosen characteristics and produces distinct breeds or varieties . The limiting factor in selective breeding is the available genetic variation in the breeding population; low variation constrains how far traits can change and increases the risk of inheriting harmful alleles.
Practical methods used
Practical methods include choosing parents with extreme or preferred traits, cross-breeding different lines to combine traits, and advanced methods such as embryo transfer and splitting to multiply valuable genotypes. Embryo transfer and splitting allow multiple offspring from high-quality parents and speed up dissemination of desirable traits in livestock . Tissue culture and controlled pollination provide rapid multiplication for plants; these methods trade genetic diversity for uniformity, which is useful for consistent crop quality but restricts adaptability.
Impact on food plants
Selective breeding in food plants produces higher yields, improved tolerance to weather and resistance to certain pests and diseases. Crops bred for uniform ripening and harvestability increase agricultural efficiency and reduce losses during harvesting and storage . Limiting factors include reduced genetic variation across crops and vulnerability to new pests, diseases or changing climates; low variation in a widely planted variety leads to large-scale crop failure if a new threat emerges.
Impact on domesticated animals
Selective breeding in domesticated animals increases productivity traits such as milk yield, meat quality and growth rate, and selects behavioural traits like docility and trainability. Livestock breeds such as high-yielding dairy cows and meat breeds illustrate direct economic effects of selection . A major limiting factor is the reduction in the gene pool, which increases the frequency of harmful alleles and predisposes breeds to inherited conditions that reduce health and welfare.
Benefits of selective breeding
Benefits include increased yield per plant or animal, improved product quality (taste, texture, nutritional content), enhanced disease or pest resistance, and production of predictable traits for commercial uses. These outcomes increase food supply and efficiency in agriculture and animal production . Economic and food-security gains depend on maintaining sufficient diversity elsewhere; selective breeding provides short- to medium-term gains but requires management to avoid long-term vulnerability.
Risks and problems, including inbreeding
Selective breeding often reduces genetic variation and causes inbreeding when parents are closely related; inbreeding increases the chance that offspring inherit two copies of harmful recessive alleles, raising incidence of genetic disorders and physical problems such as hip dysplasia in dogs . Small gene pools reduce adaptive capacity to environmental change and increase susceptibility to new diseases; for example, a breed with a very small effective gene pool may lack alleles needed to resist previously unseen pathogens, increasing risk of widespread decline .
Key notes
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