Biology - reproduction and cloning

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Cloning plants

The simplest way to clone a plant involves taking a cutting from the parent plant, removing the lower leaves and planting the cutting into damp compost. The cutting is kept in warm and moist conditions, and provided with water and minerals. Eventually (after a few weeks) new roots develop, which go on to form an entirely new plant.

An alternative way of plant cloning is tissue culture. This is where tiny pieces from the parent plant are used, and grown in petri dishes in a laboratory for a while, before being transferred into compost to allow the new plant to grow.

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Cloning animals

It is much harder and takes a lot longer to clone animals, than plants. For example; cloning sheep. A developing embryo is removed from a pregnant sheep in the early stages of the pregnancy. The cells of the embryo are seperated, and grown in petri dishes in a laboratory. The cells are then transported into host mothers. The offspring are identical to both their real genetic mother, and each other, but they are not related in any way to their host mothers, as the host mothers simply accomodate the growing embryo, and eventually give birth to it.

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Genetic engineering

Genetic engineering - or genetic modification - is where enzymes are used to cut pieces of DNA from one organism, and transfer them in to a gap in DNA in another organism. This means that the new organism will have gained one or more new characteristics from the new genetic information. A genetically modified organism is called a transgenic organism. Both plants and animals can be genetically engineered.

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The nucleus of a cell contains chromosones made from DNA. The human body has 23 pairs of chromosones from each parent. A gene is a section of DNA that carries the code for a particular protein. Offspring resemble their parents because they have genetic information passed on to them from their parents, however, they are not identical to their parents, as they have two sets of chromosones, containing two different sets of DNA. In a cell, the chromosones are found in the nucleus. Genetic information is carried by DNA. Sex cells (egg and sperm) are called gametes, and the fusion of both gametes is called fertilisation. Normal reproduction doesn't produce exact copies of the parent, whereas asexual reproduction does, because they only obtain one set of chromosones, containing one set of DNA.

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