MCAT Content / Genetics Of Prokaryotic Cells / Transformation Incorporation Into Bacterial Genome Of Dna Fragments From External Medium

Transformation: incorporation into bacterial genome of DNA fragments from external medium

Topic: Genetics Of Prokaryotic Cells

Transformation is the direct uptake, incorporation, and expression of exogenous genetic material into the bacterial genome of DNA fragments from the external medium.

Transformation is one of the three processes by which exogenous genetic material gets introduced into a bacterial cell. During transformation, prokaryotes take in DNA found in its environment that is from other prokaryotes. Bacterial transformation may be referred to as a stable genetic change brought about by the uptake of naked DNA (DNA without associated cells or proteins ). 

Transformation can happen when some species, upon cell death, release their DNA to be taken up by other cells. However, transformation works best with DNA from a closely-related species. Bacteria carry sets of genes that provide the protein machinery to bring DNA across the cell membrane. If a nonpathogenic bacterium takes up DNA for a toxin gene from a pathogen and incorporates the new DNA into its chromosome, it may become pathogenic, too.

Transformation: DNA from dead cells gets cut into fragments and exits the cell. The free-floating DNA can then be picked up by competent cells. The exogenous DNA is incorporated into the host cell’s chromosome via recombination.

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Key Points

• Transformation is a type of prokaryotic reproduction. Prokaryotes take up DNA found within their environment that has originated from other prokaryotes.

• Exogenous DNA is taken up into the recipient cell from its surroundings through the cell membrane.

• Transformation occurs naturally in some species of bacteria, but it can also be affected by artificial means in other cells.

Key Terms

transformation: the alteration of a bacterial cell caused by the transfer of DNA from another, especially if pathogenic

expression: the process by which information from a gene is used in the synthesis of a functional gene product

exogenous: produced or originating outside of an organism

naked DNA: DNA without associated cells or proteins

prokaryotes: an organism whose cell (or cells) are characterized by the absence of a nucleus or any other membrane-bound organelles

nonpathogenic: organisms are those that do not cause disease

pathogen: a bacterium, virus, or other microorganisms that can cause illness.

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