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A2 biology 5.2.1
OCR biology - cloning in plants and animals
| Question | Answer |
|---|---|
| Define: clone | Genes, cells, organisms that have identical genetic material, as they are derived from the same DNA |
| Give examples of clones produced in nature | Identical twins formed when an embryo divides in 2, asexual reproduction (CELLS/ OFFSPRING arise from a single parent): mitosis in eukaroytes, binary fission in prokaryotes, vegetative propagation |
| Define vegetative propagation + e.g.s | Form of asexual reproduction, offspring grow structures that grow into new individuals, clones. Strawberry plant =runners. Within 2 months of damage, elm trees grow root suckers/basal sprouts from meristem in base of trunk/ roots, clonal patch |
| What are the advantages of asexual reproduction? | Quick (no need for sexual organs to grow), useful if lack of gametes/mates, likely that parent will be well adapted, advantageous alleles. Vegetative propagation: elm can survive damage and clonal patch spreads far |
| What are the disadvantages of asexual reproduction? | No genetic variation, MONOCULTURE, population is unable to adapt and evolve by natural selection if the environment changes e.g. all equally susceptible to new disease. Genetic diseases are automatically inherited e..g dutch elm. |
| What are the 3 methods of artificially cloning plants? | Cuttings: cut stem between nodes, dip ends in hormones that promote root growth. Grafting: insert shoot of woody plant into rootstock. Tissue culture/ micropropagation: explant from apex, grow on nutrient agar, callus, shoots -> roots -> greenhouse |
| What are the advantages of artificially cloning plants? | Plants will have predictable features, high yield/ resistance/ good taste, plants are ready for harvesting as same time, micropropagation produces large numbers of plants from small amount of plant tissue, useful in experiments (easy to GM, results unaffe |
| What are the disadvantages of artificially cloning plants? | Monoculture = no genetic variation = unable to adapt and evolve by natural selection if the environment changes. Micropropagation is expensive: specialised equipment, aseptic technique |
| What are the 2 methods of cloning animals? | 1) fertilise egg +sperm in vitro, grow embryo, split into segments, insert into uterus of surrogate mothers, genetically identical animals. 2) diploid nucleus of differentiated adult cell->enucleated egg, stimulate with electric pulse, surrogate mother |
| What are the advantages of cloning animals? | Quickly reproduces high-value animals (high milk/meat yield, GM e.g. produces pharamacuetical chemicals in milk), clone rare animals to conserve species |
| What are the disadvantages of cloning animals? | Animal welfare issues, unsure of long-term health implications, no genetic variation |
| What is reproductive cloning? | Cloning to produce new, genetically identical ORGANISMS |
| What is non-reproductive cloning? | THERAPEUTIC CLONING: produces new, genetically identical cells, tissues and organs to replaced damaged tissues |
| Evaluate the use of non-reproductive cloning | Adv: immune system will identify new cells as 'self', no waiting on transplant list, cells are totipotent, less dangerous that major surgery. Disadv: ethical considerations in humans as embryo is killed after |
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