The second method is Spores. These are simply specialised cells that are released from the parent in large numbers to be dispersed. Each spore can grow into a new plant identical plant to its “parent”.
The final natural plant cloning method is parthenogenesis. It is used by some plants like citrus fruits and also some invertebrate animals e.g. honeybees and aphids, as an alternative to sexual reproduction. The egg cells simply develop into offspring without being fertilised. These clones can be haploid or the chromosomes could replicate making them diploid.
Cloning plants is a very big industry; brewers, farmers and plant growers all want to be able to produce and reproduce the best organisms exactly. Asexual reproduction is okay for some plants to reproduce, like potatoes, but many important plants do not reproduce asexually and so artificial methods have to be used.
Cuttings have long been used as a method of cloning plants. Part of the plant’s stem is cut and simply replanted in wet soil. Each cutting produces new roots and flowers into a new plant identical to the one it started as. Therefore the original plant can be cloned as many times as you want. One example of a plant that is commercially produced using this method is Geraniums.
Grafting is an ancient method used to clone plants. It was devised for plants that could not grow new roots when they had been treated as cuttings. Instead the stem is cut and grafted onto the roots of an already existing plant, see below:
The final technique is tissue culture or micro propagation and is more modern than the other two methods. Small samples of plant tissue are grown on agar jelly plates in a laboratory. The tissue is separated into individual cells. The cells grow into a mass of similar cells and when the correct plant hormones are added they can develop into small plantlets. These can then be planted into the ground outside were they will develop into normal sized plants. Conditions must be kept sterile at all times to prevent infections by microbes. Examples using this method of cloning are fruit trees, sugar cane and banana trees. With this method it means thousands of clones can be made quickly, all of them disease free and also cells can be modified whenever it is necessary.
Moving onto animals the first natural method is budding. In this method a copy of the parent develops as an outgrowth and then is released as a separate individual. It is also common in many plants see below:
One other natural cloning method similar to this is how identical twins come about. When one egg has been fertilised, and the egg divides into two separate eggs, each one contains exactly the same DNA hence producing identical twins with exactly the same DNA.
Animals can also be cloned artificially. Embryo Splitting is the most effective technique for cloning animals, and is done by duplicating the embryos before they have been converted into tissues. It is very expensive and so only used on “special” animals. It is most commonly used on cows and I shall use them for this example. A super female cow is fed a fertility drug that makes her produce many mature eggs. The eggs are removed from the ovaries and fertilised in vitro, with a male super cow’s sperm cell and allowed to develop for a few days until it has divided into 16 cells. (Here the cells can be split up individually, so another 16 embryos could be produced). The embryos are then implanted back into the cow’s uterus where it will develop and have a natural birth.
The final artificial method for cloning animals is by Somatic Cell Cloning. This is an advancement on embryo splitting. With embryo splitting you can not guarantee what the characteristics of the offspring will be, you can only assume that by combining a super dad and a super mum you will get a super baby. With somatic cell cloning you can clone a mature animal. Until recently it has been thought impossible to do, but in 1996 “Dolly” the sheep was cloned. For Dolly the cell was taken from the skin of the udder and was fused with an unfertilised egg which had had its nucleus removed. The combination was like a zygote and it developed into an embryo. The embryo was implanted back into a sheep’s uterus where it developed and was born naturally.
This information was provided by Peter Webster Jr.
