Cotransformation is the simultaneous

transformation Transformation may refer to: Science and mathematics In biology and medicine * Metamorphosis, the biological process of changing physical form after birth or hatching * Malignant transformation, the process of cells becoming cancerous * Tran ...

of two or more

genes In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. Only genes in the same

chromosomal A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

vicinity can be transformed; the closer together the genes lie, the more frequently they will be cotransformed. By contrast, genes sufficiently far apart that they cannot appear together on a fragment of foreign DNA will almost never be cotransformed, because transformation is so inefficient that recipient cells usually take up only a single DNA.

Example

In one study of

natural transformation In category theory, a branch of mathematics, a natural transformation provides a way of transforming one functor into another while respecting the internal structure (i.e., the composition of morphisms) of the categories involved. Hence, a na ...

, investigators isolated ''B. subtilis''

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

with two

mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosi ...

—''trpC2'' and ''hisB2''—that made them Trp- , His- auxotrophs. These double auxotrophs served as the recipient in the study, wild-type cells (Trp+ , His+ ) were the donors. In this study, the numbers of Trp+ and His+ transformants were equal. Further tests showed that 40 of every 100 Trp+ transferred

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state' ...

were also His+. Similarly, tests of the His+ transformants showed that roughly 40% are also Trp+ . Thus, in 40% of the analyzed colonies, the ''trpC+'' and ''hisB+'' genes had been cotransformed.

Explanation

Since during transformation, donor DNA replaces only a small percentage of the recipient's

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...

, why are the two ''B.subtilis'' genes cotransformed with such high frequency? Because the ''trpC'' and ''hisB'' genes lie very close together on the chromosome and are thus genetically linked. Although the donor chromosome is fragmented into small pieces of about 20 kb during its extraction for the transformation process, the wild-type ''trpC+'' and ''hisB+''

alleles An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

are so close that they often appear in the same donor DNA

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

Sequence analysis In bioinformatics, sequence analysis is the process of subjecting a DNA, RNA or peptide sequence to any of a wide range of analytical methods to understand its features, function, structure, or evolution. Methodologies used include sequence align ...

shows that ''trpC'' and ''hisB'' genes are only about 7 kb apart.

References

* {{refend Genetics