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Question
Describe briefly the following:
Origin of replication
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Solution
One of the most important components of a plasmid is the sequence of bases that initiates replication. It is known as the origin of replication (ori). This is a region of the plasmid genome that acts as a start signal for self-replication (making another copy of itself). Any portion of DNA connected to this sequence can be replicated within host cells. This characteristic is utilised to create multiple copies of linked DNA (or DNA inserts).
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RELATED QUESTIONS
Name the selectable markers in the cloning vector pBR322. Mention the role they play.
Draw a schematic sketch of pBR 322 plasmid and label the following in it:
(a) Any two restriction sites.
(b) Ori and rop genes.
(c) An antibiotic resistant gene.
Can you think and answer how a reporter enzyme can be used to monitor the transformation of host cells by foreign DNA in addition to a selectable marker?
Why is the coding sequence of an enzyme β-galactosidase a preferred selectable marker in comparison to the ones named above?
Explain the importance of ‘Selectable marker’, with the help of a suitable example.
Answer the following question.
β galactosidase enzyme is considered a better selectable marker. Justify the statement.
How does the β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.
A clone is a ______.
Which of the following statement is not true for a clone?
A cloning vector should possess which of the following characters?
- Origin of replication (Ori)
- Ability to destroy the alien DNA
- Cloning site to link the alien DNA
- The tumour inducing plasmid Ti.
- Selectable marker.
- Low molecular weight
The CORRECT combination is
Which of the following is not a cloning vector?
Plasmid pBR322 has a PstI restriction enzyme site within gene ampR that confers ampicillin resistance. If this enzyme is used for inserting a gene for β-galactoside production and the recombinant plasmid is inserted in an E.coli strain.
What does ‘competent’ refer to in competent cells used in transformation experiments?
What modification is done on the Ti plasmid of Agrobacterium tumefaciens to convert it into a cloning vector?
For selection of recombinants, insertional inactivation of antibiotic marker has been superceded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.
Describe the role of Agrobacterium tumefaciens in transforming a plant cell.
