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Vectors Based on Bacteriophage Lambda

Lambda phage can be used in genetic experiments as a vector because not all of its genome is essential for its function. This allows for the introduction of new exogenous DNA if certain requirements are met:

- Arrangement of the genes on the phage’s genome determines which parts can be removed in order to add our DNA of interest. Luckily, no complex in vitro rearrangement is needed because the central region of the lambda genome is dispensable since it controls the lysogenic properties and we need lytic one in order to successfully transfect the target cell.
- Restriction sites have to be taken into consideration since the wild type lambda phage has a lot of them which represents a problem because it limits the choice of sites for the insertion of the DNA. This can be solved by simply choosing the phage which has reduced number of sites for particular restriction enzymes. The rest of the restriction sites can be dealt with using the technique of mutagenesis in vitro, which will modify them and make them unrecognizable by restriction enzymes.

Lambda phage can be used as insertion vector, without cutting any part of its DNA out. However, this will result in the smaller DNA insert, especially since the capsid limits the size of the DNA which can be inserted to only about 2.5 kb. Insertion vectors have only one restriction site which enables DNA fragments to be inserted into their genome. λgt10 and Charon 16A are some examples of lambda-based insertion vectors, and they can accept a bit more exogenous DNA, 7.6 kb and 9 kb, respectively.

In order to increase the amount of DNA which can be inserted, scientists have developed replacement vectors which have a stuffer fragment inside themselves that can be removed, thus providing more space for our DNA of interest. Replacement vectors need at least 2 or more restriction sites, and some examples of them are EBML4 and Charon 40.