1
Question
The most important feature present in a plasmid so it can be used as a vector is
The most important feature present in a plasmid so it can be used as a vector is
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Solution
The correct option is A origin of replication
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning. Examples include plasmids.
Common features of an ideal vector include the following:
- Presence of origin of replication (ori)
- Selectable markers
- Sites for the action of restriction endonucleases (restriction sites)
- Small sizes
- Copy number
Plasmids are double stranded, circular, extra chromosomal, self replicating DNA molecules.
The most important feature in a plasmid to serve as a vector in gene cloning experiment is the presence of an origin of replication or ori site.
The ori site or origin of the replication site is a specific nucleotide sequence on the vector DNA that initiates replication, without being dependent on genomic DNA for replication. Any piece of DNA when linked to this sequence can be made to replicate within the host cells.
Recognition sites are specific nucleotide sequences, present on the plasmid DNA, that can be recognised and cleaved by restriction endonucleases for incorporation of the gene of interest.
Selectable marker is a gene in a vector that helps in the selection of transformants (host cells which have successfully taken up the foreign DNA) and non-transformants (cells which have not taken up the vector DNA).
For example, antibiotic resistance genes in the vector act as selectable markers because they confer antibiotic resistance to the transformants while the non-transformants remain susceptible to antibiotics.
Alternate selectable markers have the ability to differentiate transformants from non-transformants by insertional inactivation of the enzymes. For example, insertional inactivation of the β−galactosidase gene.
Hence the correct option is
a. origin of replication
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning. Examples include plasmids.
Common features of an ideal vector include the following:
- Presence of origin of replication (ori)
- Selectable markers
- Sites for the action of restriction endonucleases (restriction sites)
- Small sizes
- Copy number
The most important feature in a plasmid to serve as a vector in gene cloning experiment is the presence of an origin of replication or ori site.
The ori site or origin of the replication site is a specific nucleotide sequence on the vector DNA that initiates replication, without being dependent on genomic DNA for replication. Any piece of DNA when linked to this sequence can be made to replicate within the host cells.
Recognition sites are specific nucleotide sequences, present on the plasmid DNA, that can be recognised and cleaved by restriction endonucleases for incorporation of the gene of interest.
Selectable marker is a gene in a vector that helps in the selection of transformants (host cells which have successfully taken up the foreign DNA) and non-transformants (cells which have not taken up the vector DNA).
For example, antibiotic resistance genes in the vector act as selectable markers because they confer antibiotic resistance to the transformants while the non-transformants remain susceptible to antibiotics.
Alternate selectable markers have the ability to differentiate transformants from non-transformants by insertional inactivation of the enzymes. For example, insertional inactivation of the β−galactosidase gene.
Hence the correct option is
a. origin of replication
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