6.3 Cloning Flashcards
Cloning definition
The process of producing genetically identical organisms, or sections of DNA which code for a specific trait
- Types of cloning: whole organism and gene cloning
Many organisms naturally produce clones through asexual reproduction, e.g. protists and bacteria
Somatic cell nuclear transfer (SCNT)
Process of whole animal cloning
- Skin cells taken from adult being cloned are placed next to an ennucleated, unfertilised egg from an adult female
- Electric pulses are applied to cause the skin cell to fuse with the egg cell, creating an egg cell that has the genetic material of the skin cell
- The cell then divides into an early-stage embryo (blastocyst), which is implanted in a surrogate mother
- Dolly the Sheep was created this way, and this technique is also applied to plants
Plant whole organism cloning
Vegetative propagation: aseuxal reproduction in plants where new plants are grown from parts of the parent plant, such as stems, roots, or leaves, instead of from seeds
Cutting:
- A cutting or clipping of a plant is grown elsewhere on its own, and after 1-3 weeks the roots will form a new organism identical to the original organism
- E.g. Succulents are grown using cuttings
Grafting:
- Part of a plant is cut (the cutting is called the scion) and grafted onto the root stock of another plant.
- The cuts are made with the same angles, so that over time the vascular bundles of the two plants can merge and the scion will become part of the root stock.
- The root stock allows the scion to access water and nutrients, so the scion grows into a clone of the original plant
- E.g. avocados
Tissue culture:
- Plant cells are taken from a part of the parent plant and grown in nutrient medium under controlled conditions
- The cells eventually form a callus, which is then cultured in a hormone-laden medium and develops into plantlets
Plantlets can mature into fully grown plants when planted - E.g. orchids
Gene cloning
- A gene is selected and removed from the source DNA using restricton enzymes
- The gene is pasted into a vector DNA or plasmid through annealing and ligation
- The plasmid containing the gene is introduced into a host cell by the process of cell transformation
- Multiple copies fo the gene are created when the host cell reproduces
Efficiency and ethics of cloning
Effectiveness:
- Cloning is currently ineffective
- Whole organism cloning typically has a low success rate: fewer than 10% of cloned animals survive to birth. The majority of losses are due to embryonic death, failure during implantation, or the development of a defective placenta
Ethical issues:
- Offspring of cloning are genetically the same age as the original organism it was cloned from, as the telomere of the DNA used to create the clone have been naturally shortened by biological aging. So the offspring are not born at age 0.
- This harms the organism: Dolly the Sheep should have lived to 11-12 years as other Finn-Dorset sheep, but she only lived to 6.5 years of age and had to be euthanised due to severe arthritis and progressive lung disease
- Can be unethical to the surrogate mother: if the surrogate is of another species, as is the case for the cloning of some extinct organisms, the surrogate may be harmed in carrying the pregnancy to term and birthing the offspring
Assess the effectiveness of whole organisms and gene cloning
- Judgement
- Examples
- Effectiveness
- Ethics
Celia the bucardo cloning
Cloning case study
Whole organism cloning case study
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