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Do you think that clones are unusual? That we’ve been able to make them only recently? That a clone is always an independently existing animal, like the dinosaurs in Jurassic Park? That cloning should be avoided in case it ends in disaster? If you did, you might be surprised.
We are surrounded by clones: anything that reproduces asexually, such as bacteria, is a clone of its parent. Humans have also been selectively creating, growing and eating clones for many years through propagating plants by taking cuttings. You may have even eaten meat or drunk milk from a cloned animal. Cloning today, however, is sometimes seen as controversial because it is now possible to create clones from single cells which would not occur naturally – for example from mammals (and humans).
People have been cloning plants for centuries. Traditionally we used asexual reproduction (seen here in spider plants) or took cuttings - all bananas sold in the UK come from clones of plants produced from cuttings. Now we can also make clones from cell cultures, which is how orchids have become common and affordable house plants.
Cloning can mean several different things. DNA cloning refers to the creation of multiple identical copies of a gene or DNA fragment which can then be used in genetic engineering. Cloning is usually used, however, to mean the creation of a group of genetically identical cells or organisms from the same parent cell, and this is the type of cloning we will look at in more detail here. Even though clones are genetic duplicates they can still be unique: think of any identical twins that you may know – they will be clones of each other but are they exactly the same?
The cloning of plants is of immense importance in the production of crops including apples and bananas. Plant cloning in horticulture results in many plants becoming easily affordable. Orchids are a good example – they used to be extremely expensive and rare, now they are found in every supermarket. Techniques have moved on from traditional cuttings and grafting to clones made from cell cultures. Cloning means that plants which have been genetically modified to produce specific medicines or vaccines can also be reproduced fast and economically. One major problem with cloned plants is that, because they are all genetically identical, they are very vulnerable to new diseases or to climate change.
The cloning of mammals is an area of great interest in research, especially for the development of therapeutic techniques and new medicines, and is also the area which attracts the most ethical disagreements. There are three main ways of cloning mammals which all require different methods. New organisms can be created by two different processes: cloning by nuclear transfer and embryo splitting (usually used to produce identical twins, triplets and quadruplets of farm animals from a single embryo). Therapeutic cloning, in contrast, is used to create just a group of stem cells which have a medical use. This method and the use of the stem cells produced is still being developed. There have been a number of recent successful trials using cloned stem cells, and the hope is that cloned cells could eventually be used to create a replacement organ – such as a heart.