Question

Mention the important features that were incorporated in each of the following vectors:
(i) COSMIDS
(ii) Shuttle Vectors
(iii) Expression Vectors

Hint:

Vectors differ in their features depending on purpose: Cosmids for large DNA, shuttle vectors for multiple hosts, expression vectors for protein production.

Answer 1

• (i) COSMIDS:
  • Can carry large DNA inserts (up to 45 kb).
  • Contain cos sites from bacteriophage lambda for packaging into phage particles.
  • Have bacterial origin of replication and antibiotic resistance marker for selection.
• (ii) Shuttle Vectors:
  • Contain origins of replication for two different host species (e.g., E. coli and yeast).
  • Allow replication and selection in multiple host organisms.
  • Include selectable marker genes for both hosts.
• (iii) Expression Vectors:
  • Contain strong promoter sequences for high-level expression of cloned genes.
  • Have regulatory elements like operator sequences and ribosome binding sites.
  • Include selectable markers and multiple cloning sites.
  • Often possess tags (e.g., His-tag) to facilitate purification of expressed proteins.