What is the Difference Between pBR322 and pUC19

The key difference between pBR322 and pUC19 is that pBR322 is a plasmid vector that is 4361 base pairs in length, while pUC19 is a plasmid vector that is 2686 base pairs in length.

A cloning vector is a small piece of DNA that can be maintained in an organism stably. It is also a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes. A vector contains important features that allow for the convenient insertion of a foreign DNA fragment into vectors, such as restriction sites, a selectable marker, reporter gene, and element of expression. Cloning was first performed using E. coli. Cloning vectors for E. coli include plasmids, bacteriophages, cosmids, and bacterial artificial chromosomes (BAC). The most commonly used vectors are genetically engineered plasmids. pBR322 and pUC19 are two types of plasmid vectors.

CONTENTS

1. Overview and Key Difference
2. What is pBR322  
3. What is pUC19
4. Similarities – pBR322 and pUC19
5. pBR322 vs pUC19 in Tabular Form
6. Summary – pBR322 vs pUC19

What is pBR322?

pBR322 is a plasmid vector. It is one of the first widely used cloning vectors for E. coli. This vector was first created in 1977 in the laboratory of Herbert Boyer at the University of California, San Francisco. It is a circular double-stranded DNA that is 4361 base pairs in length.

Figure 01: pBR322

This plasmid vector has special features. Normally, it has two antibiotic resistance genes: gene bla encoding the ampicillin resistance (AmpR) protein and gene tetA encoding the tetracycline resistance (TetR) protein. Moreover, it contains the origin of the replication of pMB1. This plasmid vector also has rop gene that encodes a restrictor of plasmid copy number. Furthermore, this vector has unique restriction sites for more than 40 restriction enzymes. Eleven of those forty restriction sites lie within TetR gene. There are two restriction sites for restriction enzymes HindIII and ClaI within the promoter of the TetR gene. Furthermore, there are six very important restriction sites within the AmpR gene. pBR322 is a low copy number cloning vector. It approximately provides 20 plasmid copies per bacterial cell. The molecular weight of the vector is 2.83×106 daltons.

What is pUC19?

pUC19 is a plasmid vector that is 2686 base pairs in length. It is one of the series of plasmid vectors created by Joachim Messing and co-workers. The early work on this plasmid series was conducted at the University of California.  It is a circular double-stranded DNA.

Figure 02: pUC19

This plasmid vector also contains important features. It has a N terminal fragment of β glactosidase (lacz) gene. It also has a multiple cloning site (MCS) region. This region is split into codons 6 and 7 of lacz gene. MCS region provides many restriction endonucleases restriction sites. In addition to β glactosidase gene, pUC19 also encodes for an ampicillin resistance gene (AmpR). Moreover, the origin of replication is derived from plasmid pMB1. Though pUC19 is small in size, it has a high copy number (500-700 copies per bacterial cell). The molecular weight of this plasmid vector is 1.75×106 daltons.

What are the Similarities Between pBR322 and pUC19?

  • pBR322 and pUC19 are two types of plasmid vectors.
  • They are popular cloning vectors for coli.
  • Both plasmid vectors have the same origin of replication form of plasmid pMB1.
  • These vectors have multiple restriction sites.
  • Both plasmid vectors have an ampicillin resistance gene as a selectable marker.

What is the Difference Between pBR322 and pUC19?

pBR322 is a plasmid vector that is 4361 base pairs in length, while pUC19 is a plasmid vector that is 2686 base pairs in length. Thus, this is the key difference between pBR322 and pUC19. Furthermore, pBR322 is a low copy number plasmid vector, while pUC19 is a high copy number plasmid vector.

The below infographic presents the differences between pBR322 and pUC19 in tabular form for side by side comparison.

Summary – pBR322 vs pUC19

The most commonly used cloning vectors for E.coli are genetically engineered plasmids. pBR322 and pUC19 are two types of plasmid vectors. pBR322 is a plasmid vector that is 4361 base pairs in length, while pUC19 is a plasmid vector that is 2686 base pairs in length. So, this is the key difference between pBR322 and pUC19.