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Question
Which of the following is a cloning vector?
Which of the following is a cloning vector?
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Solution
The correct option is C Ti plasmid
Vector
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning. Examples include plasmids and bacteriophages.
Features of vector
The following are the common features of vector:
- Origin of replication (ori) - It is a specific nucleotide sequence that initiates replication. Due to this the vector can undergo self replication giving rise to multiple copies of the desired gene in the host cell.
- Selectable marker - It must be present for the identification of the transformants and non-transformants.
- Sites for the action of restriction endonucleases- Recognition sites for restriction enzymes help in the cleavage of the vector helping in inserting the gene of choice.
- Carrying capacity - They must carry DNA inserts into the host cells.
DNA of Salmonella typhimurium
First recombinant DNA was formed by inserting an antibiotic resistance gene into the naive plasmid of Salmonella typhimurium. Genetic material from the bacteria cannot be used directly as a vector, as it will not possess all the features of a vector and here it also carries the information for causing typhoid fever-like disease.
Ti plasmid
Ti plasmid is a tumor inducing plasmid from Agrobacterium tumefaciens. They are modified to use as vectors. In such cases the pathogenicity of the plasmid is removed and used effectively to deliver genes into plant cells.
DNA containing antibiotic resistance genes
DNA molecules used as vectors must contain an origin of replication and restriction sites along with the selectable markers like antibiotic resistance genes. Therefore the DNA only with selectable markers cannot be used as a vector.
Ori minus pBR322
pBR322 without the ori site (origin of replication) cannot replicate on its own therefore it cannot be used as a vector.
Final answer:
b. Ti plasmid
Vector
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning. Examples include plasmids and bacteriophages.
Features of vector
The following are the common features of vector:
- Origin of replication (ori) - It is a specific nucleotide sequence that initiates replication. Due to this the vector can undergo self replication giving rise to multiple copies of the desired gene in the host cell.
- Selectable marker - It must be present for the identification of the transformants and non-transformants.
- Sites for the action of restriction endonucleases- Recognition sites for restriction enzymes help in the cleavage of the vector helping in inserting the gene of choice.
- Carrying capacity - They must carry DNA inserts into the host cells.
First recombinant DNA was formed by inserting an antibiotic resistance gene into the naive plasmid of Salmonella typhimurium. Genetic material from the bacteria cannot be used directly as a vector, as it will not possess all the features of a vector and here it also carries the information for causing typhoid fever-like disease.
Ti plasmid
Ti plasmid is a tumor inducing plasmid from Agrobacterium tumefaciens. They are modified to use as vectors. In such cases the pathogenicity of the plasmid is removed and used effectively to deliver genes into plant cells.
DNA containing antibiotic resistance genes
DNA molecules used as vectors must contain an origin of replication and restriction sites along with the selectable markers like antibiotic resistance genes. Therefore the DNA only with selectable markers cannot be used as a vector.
Ori minus pBR322
pBR322 without the ori site (origin of replication) cannot replicate on its own therefore it cannot be used as a vector.
Final answer:
b. Ti plasmid
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