Cloning

In the syllabus and the exam

Cloning is the production of one or more genetically identical copies of a cell, tissue or whole organism, and at SPM level the syllabus focuses mainly on tissue culture (also called micropropagation) as the main technique studied: a small piece of plant tissue is grown under sterile, controlled conditions in a nutrient medium containing the correct balance of plant hormones, dividing repeatedly to eventually produce many complete, genetically identical plantlets from a single parent plant. Candidates should be able to explain the practical advantages of tissue culture, such as rapidly producing large numbers of disease-free plants with characteristics identical to a proven, high-quality parent plant, far faster than growing new plants from seed. A common error is confusing cloning with genetic engineering; cloning produces exact copies of existing genetic material with no new genes introduced, while genetic engineering introduces a specific new gene, often from a different species, to create a new characteristic that did not exist before. Candidates should also be aware, in balanced terms, of a limitation of cloning: because all clones share an identical genotype, an entire cloned population has no genetic variation between individuals, making it uniformly vulnerable to the same disease or environmental stress, unlike a genetically varied population produced by normal sexual reproduction. Candidates should also be able to name a second cloning technique sometimes referenced in the syllabus, such as taking cuttings for simple asexual propagation, and compare it briefly with tissue culture in terms of the scale and speed at which identical plants can be produced.

Example

Taking a small cutting from a healthy orchid plant and growing it under sterile conditions in a nutrient medium to produce many genetically identical orchid plantlets is an example of cloning through tissue culture.

Related terms

BiotechnologyGenetic engineering

Source:SRC-DSKP-EN