Human Chromosomes

Inside the nucleus our DNA is arranged into 23 pairs of chromosomes (or 22 pairs, and one X chromosome and Y chromosome if you are male). These 46 chromosomes are collectively known as the human genome, as they contain all of the genes that act as the blueprint of the human body. We can think of our DNA as a long linear molecule that is split into 46 seperate peices (i.e. the chromosomes). Within each chromosome there are thousands of genes lined up sequentially one after another, and seperated by intergenic regions. Each gene is a unit of DNA that encodes for a specific protein, with a unique function. It is the combination of many different proteins, and their actions on other molecules like sugars and lipids, that make up the basis of the organelle, and by consequence, of the cell itself, see diagram below:

So one can imagine that in a disease, where an organ is not working properly because its constituent cells are malfunctioning, we can often trace the malfunction to a faulty protein that is not performing its allocated task. These protein malfunctions can either be genetic, or acquired during (1) an infection, (2) a faulty immune response to one's own cells, (3) pre-mature tissue degeneration, or (4) the formation of cancer. So, in any circumstance where a disease, of any type, can be traced to a malfunction of a protein, or where a protein of known activity can restore the proper functioning of a cell, gene therapy can be applied. This is simply because we can now use the correct gene to deliver the correct version of the protein to the cell we want to repair. It is important to note that by delivering genes specifically into diseased cells, there is very little chance of passing this new genetic information in the future to our children. In order to do so, the cells that comprise our genetalia would have to be the target for gene transfer, a process that is illegal, and extremely technically demanding.