Molecular Genetics

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One way of physically introducing DNA into cells is as carried by liposomes.

• Liposomes are lipid-bilayer bounded vesicles. They can be formed by hydrating lipids in aqueous solutions.
• If DNA is present in the solution, DNA becomes incorporated into the liposomes.
• Liposomes interact with wall-less cells. The liposomal contents are transferred to the inside of the cell. Both membrane fusion and endocytosis have been implicated as mechanisms.
• Genes present in the transferred DNA can be expressed transiently.
• The transferred DNA may also integrate into chromosomes and cell lines containing the integrated gene may be selected.

Further Information:

• Liposomal delivery can be used with yeast and plant cells, provided their cell walls are first removed forming spheroplasts or protoplasts, respectively.
• The transfered genes will be in environments different from their normal environment and the positions of integration of the genes in different cell lines will differ.
• A variation of the liposome technique is the fusion of two cells. When this occurs between bacterial spheroplasts carrying plasmids and eukaryotic cells, the plasmids are often transferred into the eukaryotic cell environment and function there. When two eukaryotic cells are used, somatic hybrids are the result.
• In another variation, cationic lipids that interact with DNA can deliver that DNA to cells. The most efficient are lipid mixtures that form arrays in which the rod-like DNA molecules are packed in parallel in a hexagonal pattern in a lipid matrix (ref).
• Liposomes are but one way of putting DNA into living cells.