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2.1.3.5 Shuttle vectors
2.1.3.5 Shuttle vectors
Specialized vectors have been made that can replicate in more than one organism.
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This allows the same gene to be expressed in different hosts. Shuttle vectors must have separate origins of replication and separate selection mechanisms for each host organism.
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In order for a shuttle vector to grow in both yeast and E. coli, it must have several essential elements;
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two origins of replication, one for E. coli and one for yeast;
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a yeast centromere sequence so that it is partitioned into the daughter cells during yeast replication;
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selectable marker s for both yeast and E. coli; and
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a multiple cloning site for inserting the gene of interest.
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Phage has a linear DNA molecule so a single break creates two fragments.
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Foreign DNA can be inserted between them and two fragments can be joined.
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Such phages when undergo lytic cycle in host will produce more chimeric DNA .
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Wild type lambda phage could accommodate only 2.5 kb of foreign DNA.
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Phage vectors are restructured by removing nonessential genes and making vector DNA smaller so that larger insert can be accommodated in phage head during packing.
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Lambda phage such prepared has one Eco RI site and accommodates 20-25kb of foreign DNA.
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They are used for preparing genomic library of eukaryotes.
Last modified: Tuesday, 19 June 2012, 10:49 AM