Cloning

Humans have been cloning plants for centuries by taking cuttings and scientists succeeded in cloning a frog in 1958. This was followed by clones of fish in the 1960s and 1970s but it wasn't until 1997 that the first large animal, a sheep called Dolly, was cloned. Since then, other large animals have also been cloned, including pets. As the technique has been developed, it has been possible to combine cloning with genetic engineering

There are two main techniques of large animal cloning. The first involves separating the stem cells (cells which have not yet become specialized) of a naturally fertilized embryo and implanting the individual cells into a host mother. The second involves removing the nucleus from an unfertilised egg cell and replacing it with the nucleus from a donor animal.

It would be possible to create human clones in the same way but there are many ethical issues. In your middle school exam you may be asked to use your scientific knowledge of cloning to discuss the pros and cons of human cloning. If you do get such a question, make sure that you show that you know and understand the issues and offer arguments from both sides.

Now play this quiz all about cloning organisms to see how much you know about surrogates, gametes, enucleating and donors.