Biotechnology and Bioinformatics (1+1)

2.1.3.5 Shuttle vectors

Specialized vectors have been made that can replicate in more than one organism.

• 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.
• In order for a shuttle vector to grow in both yeast and E. coli, it must have several essential elements;
• two origins of replication, one for E. coli and one for yeast;
• a yeast centromere sequence so that it is partitioned into the daughter cells during yeast replication;
• selectable marker s for both yeast and E. coli; and
• a multiple cloning site for inserting the gene of interest.

• Phage has a linear DNA molecule so a single break creates two fragments.
• Foreign DNA can be inserted between them and two fragments can be joined.
• Such phages when undergo lytic cycle in host will produce more chimeric DNA .
• Wild type lambda phage could accommodate only 2.5 kb of foreign DNA.
• 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.
• Lambda phage such prepared has one Eco RI site and accommodates 20-25kb of foreign DNA.
• They are used for preparing genomic library of eukaryotes.