Victoria Nichols, of Rangi Ruru School, asks :-

When scientists are trying to form a clone of an animal how do they get the cells to multiply?

Frank Sin, a Molecular Geneticist at the University of Canterbury, responded.

When you want to obtain a clone from a single cell, you will have to consider a number of things such as where the cell is coming from, and whether it is from a normal organ/tissue or diseased organ/tissue.

Normal cells do not grow well without help. They usually die after about 20 cell divisions; some cells may go through 80 cell divisions before they become extinct. Cells are normally cultured in a nutrient rich medium supplemented with foetal calf serum. In order to enhance growth, you will have to use chemicals to stimulate cell division and cell growth.

For example, if you want to grow white blood cells (lymphocytes), you will use phytohemagglutinin (PHA) to stimulate cell division. Interlukin 2, which is a T lymphocyte growth factor, can be used to stimulate T lymphocytes growth. But it is more expensive than PHA. Different cell types will require different growth factors. If chicken or human fibroblasts are to be cultured, then you use insulin or dexamethasone (a synthetic hydrocortisone analogue) to improve colony growth.

However, if the cells are from a cancer tissue or organ, the cancer cells will grow indefinitely in a nutrient rich medium without the addition of growth factors because cancer cells have lost the mechanism for cell cycle control.

There are many established cell lines which are derived from cancer tissues. Scientists can obtain different cell lines from the American Type Culture Collection for their research.

We are using some established (immortalised) cancer cell lines to study how mutations in the mitochondria can affect cell growth. Mitochondria are tiny organelles in a cell. Their function is to produce energy in the form of ATP for the cells to carry out their work. We want to find out what would happen to a cell if there are mutations in the genes of the mitochondria that reduce the amount of energy produced by the cell. Will the cells grow slower, have fewer cell divisions or die sooner than those cells without any mutations in the mitochondria?