Why clone genes?

There are basically two reasons why geneticists want to clone genes. Both reasons require them to have thousands or millions of copies of the same DNA molecule in a test tube. Therefore, they will want to have a means of generating these copies on demand. The first motive for cloning genes may be to gain information about the nucleotide sequence of the gene. DNA sequencing or restriction enzyme cutting analysis can be used to study a gene or compare versions of a gene from different sources. A second motive would be to manipulate a gene. This means to alter the gene’s DNA sequence or combine different DNA molecules together. Why would gene manipulation be a goal for a geneticist? The geneticist may want to place the modified gene into the cells of a new organism (genetic transformation).

A living cell can be genetically transformed by putting a new gene(s) into it. Only one copy of the DNA molecule is needed to permanently change the genetic makeup of a single cell. The transformation of a cell has a greater chance of being successful when many copies of the desired gene are given the opportunity to go into the cell. The genetic engineer must have many copies of their desired gene if they expect to recover transformed plants or animals that have incorporated the gene into their own chromosomes.

The bottom line is a geneticist can only analyze or manipulate a gene if they have many copies of the gene. To obtain copies of the gene for cloning, they must first isolate the gene.

Fig.1: Cloning a gene makes it possible to obtain many copies of the same DNA molecule. The cloned DNA is copied as a circular molecule in a bacteria. (Image by D. Lee)

Fig. 2: Cloning DNA means that the original DNA molecule is copied and then new copies of copies are made using the replication process. (Image by D. Lee)