Thekey differencebetween Cosmid and Phagemid is on the type of sequences it contains.A Cosmid contains a cos site and aplasmid. Therefore, it is a hybrid vector while a Phagemid is a plasmid that contains an F1 origin of replication of the F1 phage.
Cosmids and Phagemids are used for cloning purposes, especially to clone larger fragments of DNA. These are widely used especially in cloning genes responsible for the production of various proteins. Cosmids and Phagemids are either replicated alone as plasmids or are packaged into viral particles and then replicated.
内容
1.Overview and Key Difference
2.What is a Cosmid
3.What is a Phagemid
4.Similarities Between Cosmid and Phagemid
5.Side by Side Comparison – Cosmid vs Phagemid in Tabular Form
6.概括
What is a Cosmid?
A Cosmid, referred as a hybrid plasmid, comprises cos sites extracted from Lambda phage particles and a plasmid. These cos sites are long fragments of DNA with 200 basepairs. Hence, they have cohesive or sticky ends that allow the plasmid to fit into the viral DNA. Therefore, the cos sites are vital for packaging of the DNA.
有三个COS站点；
- COSN站点 - 参与末端酶活性划分DNA链
- COSB站点 - 持有终端酶。
- cosQ site – involved in preventing the degradation of the DNA byDNases.
Figure 01: Cosmid
同样，宇宙可以使用合适的复制起源来复制单链DNA或双链DNA。宇宙通常包含抗生素抗性基因作为选择转化体的标志物。因此，使用宇宙作为向量可以促进克隆，并且向量的限制酶消化可以提取这些片段。
What is a Phagemid (Phasmid)?
Phagemid, also termed asPhasmid，也是一种混合矢量。吞噬作用包含一个特殊的复制起源，称为复制的F1起源。从F1噬菌体提取复制的F1起源。
Phagemid can replicate both single-stranded and double-stranded DNA. Replication can either take place as a plasmid while undergoing independent replication or can get packaged into phage particles and finally infect bacterial hostE coli. When infecting theE colicells, the f1 phage requires the presence of apilus. Hence, the sex pili are important during体外吞噬的包装。
What are the Similarities Between Cosmid and Phagemid?
- Both Cosmid and Phagemid are cloning vectors used in重组DNA技术.
- Cosmid and Phagemid can replicate single-stranded and double-stranded DNA.
- Both can undergo independent replication similar to plasmids.
- Cosmid and Phagemid can undergo体外packaging and infect bacterial cells.
- 宇宙和吞噬作用都需要合适的复制起源来克隆。
宇宙和吞噬作用有什么区别？
Cosmid vs Phagemid |
|
| Cosmid是一个杂种矢量，其中包含一个COS位点和质粒。 | 吞噬是一种质粒，其中包含F1复制的F1起源。 |
| Presence of Cos Sites | |
| COS位置存在于宇宙中，对于体外包装是必需的。 | Cos sites are absent in phagemid. |
| F1的起源的复制 | |
| In cosmid, fi origin of replication may or may not present. | F1 origin of replication is present in phagemid. |
| Presence of Antibiotic Resistant Genes | |
| Antibiotic-resistant genes are present in cosmids to identify the transformants from non – transformants. | 吞噬作用中不存在抗生素耐药基因。 |
| 体外包装的需求 | |
| Requires a cos site. | Requires a sex pilus. |
概括–Cosmid vsPhagemid
Cosmid and Phagemid are cloning vectors used in recombinant DNA technology. Cosmids are hybrid vectors that contain special sticky ends known as cos sites.in-vitro包装要求uire these cos sites. While phagemids are plasmids that contain an f1 origin of replication extracted from f1 phage. Both cosmid and phagemid can undergo independent replication or体外packaging to bacterial cells. These are the important differences between cosmid and phagemid.
Reference:
1.Qi, H, et al. “Phagemid Vectors for Phage Display: Properties, Characteristics and Construction.” Journal of Molecular Biology., U.S. National Library of Medicine, 30 Mar. 2012.Available here
2.Collins, J, and B Hohn. “Cosmids: a Type of Plasmid Gene-Cloning Vector That Is Packageable in Vitro in Bacteriophage Lambda Heads.” Proceedings of the National Academy of Sciences of the United States of America, U.S. National Library of Medicine, Sept. 1978.Available here
Image Courtesy:
1.’Cosmid (English)’By Zlir’a (CC0) viaCommons Wikimedia
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