A vector is any DNA molecule that has the ability to replicate inside the host to which the desired gene has integrated for cloning.

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Vectors include plasmids, bacteriophages, cosmids, BAC, YAC, yeast vectors, shuttle vectors etc.

Difference between BAC and YAC
YAC and BAC vectors are two genetically engineered artificial vectors designed to clone large DNA fragments. Now both these vectors are very much modified based on requirements. Let’s differentiate the basic YAC and BAC vector in this post.



YAC vector means Yeast Artificial Chromosome vectors.

BAC vector means Bacterial Artificial Chromosome Vectors.

Developed by Burke and Olson in 1987

Developed  Melsimon et al 1992

  • Can replicate inside yeast
  • Used to clone DNA sequences in yeast cells

  • Can replicate inside bacteria
  • used to clone DNA sequences in bacterial cells

Basic Components of YAC vector

  • ARS (Autonomously Replicating Sequence)  – Ori; origin of replication for Yeast
  • CEN (Centromeric) –yeast centromere for  movement of YAC vectors  to daughter cells
  • 2 TEL (Telomeric) -Telomeric region for behaving as yeast chromosome on linearization
  • AmpR– Selectable marker genes for selection of transformed cells
  • BamHI and EcoRI restriction sites for inserting our gene of interest

  • Basic components of BAC vector(pBAC108L first developed BAC vector)
  • OriS – ori for bacteria repE – initiation & assembly of the replication  complex 
  • parA and parB – movement of BAC to daughter cells
  • Selectable marker –Chloramphenicol Resistance for selection of transformed cells
  • T7 and SP6 – Promote transcription of insert gene  


Its construction is based on regions of yeast chromosome like ARS

BAC is a DNA construct, based on functional fertility plasmid (or F-plasmid), of  E. coli.

  • Linear vector inside yeast cell with 2 telomeric ends
  •  just functions as yeast chromosomes without disturbing original chromosomes

Circular vector inside the bacterium

Clone DNA fragments larger than 100 kb and up to 3,000 kb

Insert size is 150–350 kb.

  • It is used for physical mapping and sequencing of genomes. YAC libraries of human and Caenorhabditis elegans and many genomes
  • First used in Human genome project later shifted to BAC vectors due to stability issues with YAC

  • It is used for physical mapping and sequencing of genomes.
  • Used in HGP and in physical genetic maps of including Mus musculus, Arabidopsis thaliana, and Homo sapiens.

Advantage of YAC: large insert size


Advantage of BAC: More stable than YACs, and easy to manipulate compared to YAC

Disadvantage: Less stable than BAC and produce chimeric effects (deletion and inversion of cloned sequences)

Disadvantage: Small insert size compared to YAC

Reference: Bajpai B. (2013). High Capacity Vectors. Advances in Biotechnology, 1–10.

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