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प्रश्न
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?
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उत्तर
Transformation is the process of introducing a fragment of DNA into a host bacterial cell. Normally, genes encoding antibiotic resistance, such as ampicillin and tetracycline, are considered useful selection markers for discriminating between transformed and non-transformed bacterial cells. In addition to these selectable markers, another selectable marker has been designed to distinguish between transformed and non-transformed bacterial cells based on their ability to produce colour in the presence of a chromogenic material. A recombinant DNA is inserted into the coding sequence of β-galactosidase, a reporter enzyme. If the plasmid in the bacterium does not have an insert, the presence of a chromogenic substance gives blue-coloured colonies. The presence of an insert results in insertional inactivation of β-galactosidase and, therefore, the colonies do not produce any colour. These colonies are marked as transformed.
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संबंधित प्रश्न
State how has Agrobacterium tumifaciens been made a useful cloning vector to transfer DNA to plant cells.
Write the role of ‘restriction sites’ in the cloning vector pBR322.
What is ‘Ori’ ? State its importance during cloning of a vector.
Explain the importance of ‘Selectable marker’, with the help of a suitable example.
How does the β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.
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?
Describe the role of CaCl2 in the preparation of competent cells?
Name the regions marked A, B and C.
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.
The figure below shows the structure of a plasmid.
A foreign DNA was ligated at BamH1. The transformants were then grown in a medium containing antibiotics tetracycline and ampicillin.
Choose the correct observation for the growth of bacterial colonies from the given table.
The following diagram showing restriction sites in E. coli cloning vector pBR322. Find the role of ‘X’ and ‘Y’ genes:
The “Ti plasmid” of Agrobacterium tumefaciens stands for ______.
Which of the following is not a cloning vector?
What is the primary function of a vector in recombinant DNA technology?
What is the basic biological nature of plasmids when used as cloning vectors?
