B1.4 How is a clone made?
Clones are genetically identical individuals. Bacteria, plants and some animals can reproduce ASEXUALLY to form clones that are genetically identical to their parent. ASEXUAL REPRODUCTION only requires one parent, unlike sexual reproduction, which needs two. Since there is only one parent, there is no fusion of gametes and no mixing of genetic information. As a result are genetically identical to the parent and to each other.
Identical human twins are also clones – ANY DIFFERENCES BETWEEN THEM ARE DUE TO ENVIRONMENTAL FACTORS.
Plants- asexual reproduction in plants can take a number of forms:
Some plants such as strawberries produce shoots called RUNNERS. These eventually break off and become new strawberry plants, clones of the original.
Other plants grow BULBS. When bulbs are planted they grow into genetically identical plants. Again the environment will alter them. No two organisms can occupy the same space in the universe so the environment will always be different for individuals, even if they are clones.
Animals – clones in animals can occur naturally and artificially:
Clones of animals occur naturally when, during the earliest stages after fertilisation, the developing embryo splits into two, they have the same genes. As the genes came from both parents they are not clones of either parent, but they are natural clones of each other.
It is now possible to make clones artificially by taking the nucleus from an adult body cell and transferring it into an empty, unfertilised egg cell.
Cloning depends on cells that have the potential to become any cell type in the body. These are called STEM CELLS.
ADULT STEM CELLS are unspecialised cells that can develop into many, but not all types of cell.
EMBRYONIC STEM CELLS are unspecialised cells that can develop into ANY type of cell, including more embryonic stem cells.
As a result of being unspecialised, stem cells from embryos and adults offer the potential to treat some illnesses.
For example – skin can grow as a treatment for serious burns and sight can now be restored to people who are blind due to damage of their corneas.
The majority of cells of multicellular organisms become specialised during the early development of the organism. This is because after the zygote has divided four times to reach the 16 cell stage, the majority of cells in the embryo start to become specialised.