Transformation (genetics) facts for kids

In molecular biology, transformation is when a cell changes its genetic makeup. This happens when the cell directly takes in DNA from its surroundings. Then, it starts using this new DNA.

Transformation can happen naturally in some types of bacteria. Scientists can also make it happen artificially in labs. Bacteria that can take in DNA, either naturally or artificially, are called competent.

Transformation is one way bacteria can get new genetic material. The other two ways are conjugation and transduction. Conjugation is when two bacteria connect and share DNA. Transduction is when a bacteriophage (a virus that infects bacteria) injects DNA into a cell.

The term "transformation" can also describe putting new DNA into other cells. This includes animal and plant cells. But for eukaryote cells (cells with a nucleus), this process is usually called "transfection".

How Scientists Discovered Transformation

Transformation was first shown in 1928 by a British scientist named Frederick Griffith. He was studying a type of bacteria called Streptococcus pneumoniae. Griffith found that a harmless type of this bacteria could become dangerous. This happened after it was mixed with a dangerous type that had been killed by heat.

The Transforming Principle

Griffith thought something from the heat-killed bacteria made the harmless ones dangerous. He called this a "transforming principle." In 1944, three scientists found out what this principle was. They were Oswald Avery, Colin MacLeod, and Maclyn McCarty. They discovered it was DNA.

They took DNA from the dangerous bacteria. Then, they used only this DNA to make harmless bacteria dangerous. They named this process of bacteria taking in DNA 'transformation'. You can learn more about this in the Avery–MacLeod–McCarty experiment.

Transformation Becomes Routine

At first, other scientists were not sure about these findings. But later, other ways of transferring genes were found. Joshua Lederberg discovered conjugation in 1947. Then, transduction was found in 1953. After these discoveries, Avery's experiments were accepted.

Transformation became a common method in labs in 1972. This was when a scientist named Cohen successfully transformed Escherichia coli bacteria. He did this by treating them with calcium chloride. This made transformation easy and efficient. It opened the door for biotechnology and new research.

Transforming Animal and Plant Cells

Scientists also started to transform animal and plant cells. The first transgenic mouse was made in 1982. This mouse had a gene for rat growth hormone injected into its embryo.

In 1907, a bacterium called Agrobacterium tumefaciens was found. This bacterium caused tumors in plants. In the early 1970s, scientists found that a piece of DNA called a Ti plasmid caused these tumors. Researchers learned to remove the tumor-causing genes from this plasmid. Then, they added new genes. They could then infect plants with A. tumefaciens. The bacteria would insert the chosen DNA into the plant's own genome.

Not all plant cells can be infected by A. tumefaciens. So, other methods were created. These include electroporation and micro-injection. Electroporation uses electricity to make tiny holes in cells. Micro-injection uses a very tiny needle to put DNA directly into cells. Another method, particle bombardment, became possible in 1990. This was when John Sanford invented the Biolistic Particle Delivery System, also known as the gene gun.

See also

In Spanish: Transformación (genética) para niños