transfer of dna between bacterial cell

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TRANSFER OF DNA BETWEEN BACTERIAL CELLSThe transfer of genetic information from one cell to another is occur by three methods:




Medical ViewpointFrom a medical viewpoint, the most important two consequences of DNA transfer are:That antibiotic resistance genes are spread from one bacterial gene to another primarily by CONJUGATIONANDThat several important exotoxins are encoded by bacterial genes and are transferred by TRANSDUCTION


Definition: It is the process of gene transfer via sex pili between cells of opposite mating types that are in physical contact (cell-to-cell) with each other.


Requires the presence of a special plasmid called the F plasmid. Bacteria that have a F plasmid are referred to as F+ or male. Those that do not have an F plasmid are F- or female.The F plasmid consists of 25 genes that mostly code for production of sex pilli. A conjugation event occurs when the male cell extends his sex pilli and one attaches to the female.This attached pilus is a temporary cytoplasmic bridge through which a replicating F plasmid is transferred from the male to the female. When transfer is complete, the result is two male cells.When the F+ plasmid is integrated within the bacterial chromosome, the cell is called an Hfr cell (high frequency of recombination cell).

Conjugation in E. coli

Conjugation continued

Conjugation continued

Transduction Transfer of DNA by mean of bacteriophage.Bacterial DNA is incorporated into virus particle and is carried into recipient cell during infection.Phage DNA integrated into cell DNA and cell acquire new trait (lysogenic conversion).Non-pathogenic change into pathogenic.Diphtheria toxin, botulinum toxin, cholera toxin and erythrogenic toxin are encoded by bacteriophages and is transferred by transduction.

Transformation Transformation is a transfer of DNA from one cell to another.DNA is injected into the nucleus of eukaryotic cell is called transfection.Transfection

(used in genetic engineering procedures)DNA extracted from encapsulated smooth pneumococci transform non capsulated rough pneumococci.


Once the DNA is transferred from a donor to a recipient cell by one of three processes just described, it can integrate into host chromosome by recombination.

Types of Recombination

There are two types of recombination:Homologous recombinationNonhomologous recombination

Homologous recombination, in which two pieces of DNA that have extensive homologous regions pair up and exchange pieces of DNA by breakage and reunion.

Homologous Recombination

Nonhomologous Recombination

Nonhomologous recombination in which little if any homology is necessary.

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