Directions : In the following questions a statement of assertion (A) i...
Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
The Ti plasmid (tumour-inducing plasmid) of Agrobacterium tumefaciens is used as a cloning vector. Ti plasmid integrates a segment of its DNA, termed T-DNA into the chromosomal DNA of its host plant cells. This is the mechanism that allows for the transfer of genetic information from the plasmid to the plant cell, which is used to genetically modify the plant. The T-DNA region contains genes that are responsible for the formation of a tumour and also contains genes that can be used for genetic engineering. Therefore, the reason (R) explains the assertion (A) correctly.
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Directions : In the following questions a statement of assertion (A) i...
Assertion (A): Ti plasmid (tumour-inducing plasmid) of Agrobacterium tumefaciens is used as a cloning vector.
Reason (R): Ti plasmid integrates a segment of its DNA, termed T-DNA into the chromosomal DNA of its host plant cells.
Explanation:
The statement is asserting that the Ti plasmid of Agrobacterium tumefaciens is used as a cloning vector. The reason given is that the Ti plasmid integrates a segment of its DNA, known as T-DNA, into the chromosomal DNA of its host plant cells. Let's break down the explanation and evaluate whether the assertion and reason are true and whether the reason is a correct explanation for the assertion.
Understanding the Assertion:
To understand the assertion, we need to know what a cloning vector is and whether the Ti plasmid meets the criteria for being a cloning vector.
A cloning vector is a DNA molecule used to carry foreign genetic material into a host organism, where it can be replicated and expressed. It should have specific features like an origin of replication, selectable markers, and a multiple cloning site. These features allow the insertion and propagation of foreign DNA.
The Ti plasmid is a natural cloning vector that is used extensively in plant biotechnology. It is derived from Agrobacterium tumefaciens, a soil bacterium that causes crown gall disease in plants. The Ti plasmid has all the necessary features of a cloning vector, making it suitable for genetic engineering and transformation of plants.
Evaluating the Assertion:
The assertion (A) is true since the Ti plasmid is indeed used as a cloning vector in plant biotechnology.
Understanding the Reason:
Now let's evaluate the reason provided for the assertion. The reason states that the Ti plasmid integrates a segment of its DNA, known as T-DNA, into the chromosomal DNA of its host plant cells.
Agrobacterium tumefaciens has a unique ability to transfer a portion of its Ti plasmid, called the T-DNA, to the genome of the host plant cells it infects. This transfer occurs through a process called "transformation." The T-DNA contains the genes responsible for the formation of the characteristic crown gall tumors in plants.
Evaluating the Reason:
The reason (R) is true since the Ti plasmid does integrate a segment of its DNA (T-DNA) into the chromosomal DNA of its host plant cells.
Reason as an Explanation for the Assertion:
The reason provided is a correct explanation for the assertion. The integration of T-DNA into the host plant's genome allows for the transfer and expression of desired genes in the plant cells. This integration is a crucial step in the genetic engineering process, where foreign genes can be inserted into the T-DNA region of the Ti plasmid and transferred into plant cells. Once integrated, the foreign genes can be expressed and produce the desired traits in the transformed plants.
Therefore, both the assertion (A) and reason (R) are true, and the reason correctly explains why the Ti plasmid is used as a cloning vector. The correct answer is option C.
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