Gene Transfermation of Tumor Cells

Changes in the Genetic Makeup of a Normal Cell

Illustration representing a viral vector: utilising a virus ability to transfer its genome into a host cell, specific sequences can be introduced to destination cells as in gene therapy, vaccination or genetic modification
••• Laguna Design/Oxford Scientific/Getty Images

In genetic research, transformation is the process by which the genetic makeup of an organism is altered by the insertion of a new gene (or exogenous DNA) into its genome.

What Is DNA?

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.

What Is a Gene?

A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes.

Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people. Alleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each person’s unique physical features.


Transformation is usually done using what are known as vectors, such as plasmids, transposons, or viruses (i.e., retroviruses). These vectors can be used to insert foreign DNA into cells, and sometimes right into the chromosome of the host cell. In the context of cancer research, transformation means the process by which a normal cell is altered and begins behaving like a tumor cell.

For example, after transformation, expression of the new gene in the bacterial cells was detected using a protein assay.


Genetics Home Reference. What is DNA? U.S. National Library of Medicine.