Cloning methods and implications in biology
Inheritance, variation and evolution • Variation and evolution
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Tissue culture and plant cuttings
Tissue culture removes small sections of plant tissue or individual cells and places them on sterile nutrient agar or liquid medium with growth hormones so new plantlets develop in vitro. Sterile conditions prevent contamination and allow monitoring of growth; plantlets transfer to soil when large enough, producing many clones of the parent plant . Taking cuttings involves removing a section of stem or leaf and encouraging root formation in soil or water; cuttings require less equipment than tissue culture but offer fewer simultaneous clones and higher risk of disease transmission. Tissue culture suits industrial-scale propagation because it produces many identical, disease-free plants rapidly under controlled conditions .
Embryo transplants and embryo splitting
Embryo transplant involves fertilising ova in a donor, collecting embryos, and transferring selected embryos to recipient mothers to produce offspring genetically identical to the donor pair. Embryo splitting creates demi-embryos (twins) by dividing an early embryo before implantation, increasing numbers of identical offspring from desirable parents . Cause → effect: Superovulation in a donor cow causes several ova to develop; fertilisation and embryo collection cause multiple embryos to exist; splitting or transplanting those embryos causes multiple genetically similar calves to be produced, which accelerates propagation of desirable traits in a herd .
Adult cell cloning (somatic cell nuclear transfer)
Adult cell cloning uses a diploid somatic-cell nucleus transferred into an enucleated ovum; an electric pulse stimulates the ovum to divide and develop into an embryo that is genetically identical to the nucleus donor. The technique produces whole animals that match the adult donor genome rather than a mix from two parents, as demonstrated by Dolly the sheep . Limiting factors include low success rates, potential developmental abnormalities, and high costs. Cause → effect: Using a differentiated adult nucleus causes reprogramming requirements in the egg; incomplete reprogramming causes developmental failure or health problems in clones .
Benefits of cloning in agriculture and medicine
Cause → effect: Cloning allows rapid multiplication of individuals with valuable traits, so desirable genetics spread quickly through a population; identical high-yield plants or animals reduce time needed to establish uniform stock and can increase productivity for farmers and growers . Medical benefits include producing animals engineered to secrete human proteins in milk for therapeutic use and using cloned tissues or cells for research and potential regenerative medicine. Genetic modification combined with cloning provides reliable production systems for medical proteins and may improve access to treatments such as clotting factors produced in animal milk .
Risks, genetic diversity and ethical considerations
Cause → effect: Cloning reduces genetic diversity because many genetically identical individuals replace more varied populations; low diversity increases vulnerability to disease outbreaks and environmental change, which can cause large-scale losses in crops or livestock populations . Other risks include the spread of engineered genes into wild populations, causing ecological imbalance, and medical risks from developmental abnormalities and immune rejection. Ethical and social concerns arise from animal welfare, long-term effects of cloning, and debate about human applications; these concerns affect regulatory decisions and public acceptance .
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