Key Difference – YAC vs M13 Phage Vector
DNA cloning is an important process which enables the propagation of important DNA fragments of organisms. It requires joining of specific DNA with vector DNA to create recombinant DNA which transforms into the host organism. A vector is a DNA molecule which behaves as a vehicle to carry foreign genetic material into another cell or organism. It should be capable of replicating inside the host organism and producing multiple copies of recombinant DNA. There are different kinds of vectors used in DNA cloning. Yeast artificial chromosome (YAC) and M13 phage vector are two types among them. The key difference between YAC and M13 phage vector is that YAC is an artificial chromosome which replicates in yeast cells while M13 phage vector is a single stranded circular DNA of bacteriophage M13 which replicates in E Coli cells.
CONTENTS
1. Overview and Key Difference
2. What is YAC
3. What is M13 Phage Vector
4. Side by Side Comparison – YAC vs M13 Phage Vector
5. Summary
What is a YAC Vector?
YAC is an artificially built chromosome which has the ability to carry a large segment of foreign DNA and replicate within the yeast cells. It has centromere, telomere and autonomously replicating sequences essential for replication and stability. YAC should also bear a selective marker or markers and restriction sites to make it an effective cloning vector. Large sequences ranging from 1000 kb to 2000 kb can be inserted into YAC and transferred into yeast.
Figure 01: YAC Vector
What is M13 Phage Vector?
Bacteriophage M13 is a virus which infects and replicates in E Coli. The genome of the M13 bacteriophage is small in size, about 6.7 kb. It is a single-stranded, circular and positive sense DNA. This virus specifically infects E Coli bacteria through F pilus. Once it enters the ssDNA into the bacterium, it synthesizes its complementary strand and becomes dsDNA or the replicative form (RF) of M13. RF can behave like a plasmid within the host organism. The dsDNA replicates within E Coli and produces ssDNA bearing new phages. These new phages are continuously released from the E Coli without killing the host cell. However, the infection slows down the growth of E Coli. dsDNA can be extracted from bacterial cells and used as vectors in DNA cloning. They are known as M13 phage vectors. They can be easily manipulated and used similarly to plasmid vectors.
The inherent ability of infection of these M13 phages serves as a good qualification to be used as a vector in gene cloning. When developing M13 into a vector, several elements should be incorporated into its genome. They are, a gene for the lac repressor (lac I) protein, the operator-proximal region of the lac Z gene, a lac promoter and a multiple cloning site (polylinker). When dsDNA of the M13 is used as vectors, it can be treated as a plasmid vector. However, the use of ssDNA M13 has advantages in DNA sequencing and site-directed mutagenesis.
Since M13 phage vector bears multiple cloning site in lacZ region, recombined vectors can be easily identified by the blue/white colony screening on agar plates containing IPTG and X-Gal. Blue plaques produced on the plates do not contain the recombined phages. Therefore, phages with inserts can be selected for the cloning purpose.
Figure 02: Bacteriophage M13
What is the difference between YAC and M13 Phage Vector?
YAC vs M13 Phage Vector |
|
| YAC is a genetically engineered chromosome which has the ability to carry a large segment of foreign DNA and replicate within the yeast cells. | M13 phage vector is a viral vector developed by bacteriophage M13 which is used to insert foreign DNA into E Coli. |
| Purpose | |
| YACs were designed to clone large fragments of genomic DNA into yeast. | M13 phage vectors are used to insert foreign DNA into E Coli. |
| Insert Length | |
| YACs can contain megabase-sized genomic inserts (1000 kb – 2000 kb). | The size of inserts is about 1,500 bps. |
| Construction | |
| YAC DNA is difficult to purify intact and requires a high concentration for generating YAC vector system. | It occurs via cyclic photosynthetic electron chain. |
| Stability | |
| YAC is unstable. | M13 phages can be easily extracted. |
| Size | |
| Enzymes are larger molecules. | M13 phages are stable than YAC. |
Summary – YAC vs M13 Phage Vector
YAC is an artificially constructed vector system using a specific region of yeast chromosome to insert large segments of genetic material to yeast cells. M13 phage vector is a vector system derived from bacteriophage M 13 which uses E coli as the host organism. This is the main difference between YAC and M13 Phage Vector. Both are equally useful in recombinant DNA technology and gene cloning.
Reference:
1.”Vector.” Genetics-notes – Vector. N.p., n.d. Web. 16 May 2017. https://genetics-notes.wikispaces.com/Vector
2.”Yeast artificial chromosome.” Wikipedia. Wikimedia Foundation, 21 Apr. 2017. Web. 16 May 2017. <https://en.wikipedia.org/wiki/Yeast_artificial_chromosome>.
Image Courtesy:
1. “M13B” By J3D3 – Own work (CC BY-SA 3.0) via Commons Wikimedia