Cloning and Genetic Engineering

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Cloning and Genetic Engineering

We now know a lot about genes, chromosomes and the inherited diseases that can occur.

We also know how to use genetics to plan our selective breeding programmes to be most effective.

Cloning techniques and genetic engineering allow many new opportunities but also carry challenges.

There is both natural and artificial cloning. Both produce clones, plants that are genetically identical to the parent plants.

Natural cloning

Clones occur naturally in plants. It can occur when plants such as the strawberry send out runners, which establish a whole new plant.

strawberries

If you plant an old potato it will grow into a clone of the original.

Yet another example is plants such as daffodils, which produce bulbs. Quite often they split into two bulbs with each plant becoming a clone of the other.

The cloning process occurs through cell division mechanism of mitosis. It therefore allows them to undergo this form of asexual reproduction.

However, these plants can also reproduce using sexual reproduction (that is releasing gametes). This is important as it allows for genes to be shared between different individuals and then on to their offspring. This avoids the loss of genetic variation, which is the main problem of cloning.

Artificial cloning

For many years, gardeners have sat hunched in potting sheds around the world taking cuttings. A small piece of branch or stem is cut from a larger plant and is perhaps dipped into an auxin rooting powder. In a few weeks a new plant develops.

In a few weeks a new plant develops. Little do these humble gardeners realise that they are carrying out a form of micropropagation. This is a high-tech version of the traditional cutting approach.

In micropropagation, cuttings are taken from a stem and cut into smaller sections. Each section is sterilised first before adding them to a growth medium containing rooting hormones. After each develops roots it grows intoa plantlet. Finally, they are hardened up by being grown in a greenhouse.

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Tissue culture is another new technique that has been used for cloning plants. Here, only a few plant cells are needed. These are then added to the growth medium and hormones. They will develop into a new plant.

The advantages: the new systems are that they can produce new plants very quickly, in large numbers and in a small space. Also, they can grow inside all year round and within a controlled, disease-free environment.

The disadvantages: are that using cloned plants you face reducing the gene pool and therefore increasing the vulnerability to diseases.

While cloning does occur naturally within animals, it is less common. Cloning is usually restricted to cells dividing by mitosis, and cells splitting as is the case of identical twins.

However, a new technique of embryo transplantation has been used, especially in farming and zoos.

The eggs and sperm are checked to ensure that they are free from genetic defects. Also, it is possible to separate the sperm into those that contain a Y chromosome from the slightly heavier ones containing X chromosomes. By doing this, the final sex of the offspring can be chosen. (Y-containing sperm will give a bull calf, an X-containing one will give a female).

The advantages: your best cow and bull can artificially produce hundreds of 'perfect' calves every year rather than the usual single one. The original 'best cow' can have her eggs implanted into other cows all year round.

The disadvantages: the usual reduced gene pool and disease vulnerability.

The most radical and potentially useful new technique is genetic engineering.

This technique has already been used to produce large quantities of human insulin using bacteria. It has been a great help to sufferers of diabetes.

It has been a great help to sufferers of diabetes.This process avoids the older method of extracting insulin from dead bodies or pigs. That wasn't a very attractive idea if you had to inject yourself with insulin every day!

In genetic engineering the gene that you want is cut out of a human chromosome using special enzymes.

The gene is then fitted ('spliced') into a length of DNA from a bacterial cell and then reintroduced back into the bacterial cell.

The bacteria is tricked into carrying out the instructions on the human gene and producing the protein, insulin.

Once the bacteria has been cultivated so that it multiplies many times, enough insulin is produced so that it can be filtered off and collected.

This whole process is carried out on an industrial scale so that masses of insulin is produced in a continuous process.

There is a big debate at the moment over whether we should introduce human genes into animal embryos.

This would allow us to make things like other hormones and collect them from the animals milk.

This whole area is open to a big debate, covering scientific, social and ethical issues.

It's a good idea for you to understand all this so that you can join the debate!

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