Knowledge gained through this research will allow scientists and doctors of the future to prevent or treat most diseases at the level of genes. While it is now common to screen infants for inherited genetic diseases, further understanding of the human genome will allow doctors to determine a person's chances of developing particular diseases later in life. They will then be able to give advice or treatment to prevent, slow or cure those diseases. Identical twins are natural clones from the one fertilized egg. A plant cutting is a clone of the original plant.
Some confusion arises because the word clone is also applied to genes.
A gene is said to be cloned when its sequence is multiplied many times in a common laboratory procedure. The cloning of a gene is a step in determining its sequence and initiating many types of experiments to understand its function and biology. Dolly was produced by injecting a nucleus from a mammary cell into an egg cell without a nucleus and raising an animal from that egg by treating it as a fertilised egg. Dolly is therefore a genetic clone of the animal from which the nucleus was taken. The important difference from identical twins is that the donor was a mature sheep and could even be made the mother of the clone.