Gene Therapy to Treat Disease - Biotechnology and Your Health: Pharmaceutical Applications - page 86

VECTORS: GETTING GENES INSIDE CELLS
The system used to deliver the desired gene into the cells, called the
gene therapy vector, may be a virus, a plasmid, or even just the
“naked” DNA. The choice of vector is based on the difficulty of
getting the gene into the cell, the amount of DNA the vector can
carry, the size of the gene sequence needed to provide the correct
protein, and the effects the vector may have on the body. Each
type of vector has advantages and disadvantages.
Viruses are very important as gene therapy vectors. Over the
millennia of their existence, they have evolved to be very good at
The Human Genome Project
The Human Genome Project is a decades-long international effort by hundreds of
laboratories and thousands of scientists to determine the sequence of human DNA, at
least the part that codes for functional genes, working with robots and computers. The
human genome is 3 billion base-pairs long, but surprisingly, contains only about 25,000
genes to direct the production of the 100,000 or so proteins in our bodies. Many genes
can code for different proteins by cutting and pasting different parts together. The genome
of any individual human differs from that of another by less than 0.1%, and the human
genome differs from that of chimpanzees by only 2%, which suggests that even very small
differences may have very big impacts.
The completion of the Human Genome Project has set the stage for the discovery
of new ways to diagnose and treat diseases, and new ways to predict who will develop a
particular disease. But this will require not only a file with the bases all in a row, but an
understanding of how the genes are organized within that sequence and how the genes
that make proteins are read.
Just as the entire genetic makeup of an organism is called the genome , the entire
set of proteins that an organism makes is called the proteome . Scientists are working to
understand how and where each protein works, and how different proteins interact with
each other. To produce a complicated working body of 3 billion cells—a body that can
see, hear, walk, talk, feel, and eat—means that the cells, genes, and proteins must inter-
act well together from the time of conception to our last breath. Researchers seek to
understand how these processes are orchestrated and what goes wrong when we get ill.