Question

Q. Which of the following statements is/are incorrect about Ti plasmid?

Select the correct answer using the code given below:

• A. 1 and 3 only
• B. 3 only
• C. 1 and 2 only
• D. 1, 2 and 3

Answer 1

The correct option is B 3 only

Explanation:

Statements 1 and 2 are correct: A tumour inducing plasmid is a plasmid found in pathogenic species of Agrobacterium. Evolutionarily, the Ti plasmid is part of a family of plasmids carried by many species of Alphaproteobacteria.

The main characteristics of Ti plasmid are:

• The size of the plasmid is ~ 250kbp.
• There are different kinds of Ti plasmids based on the different genes they possess, which code for different opines, e.g. leucinopine, nopaline, octopine, etc.
• It is a pathogenic species to many dicotyledonous plants. It causes crown gall disease in plants.
• It contains one or more T-DNA regions.
• Agrobacterium tumefaciens can transform the normal cells into tumour cells by inserting a DNA piece known as T DNA and it starts producing chemicals that are required by the bacterium.
• After inserting the desired gene into the Ti plasmid, it loses its pathogenic ability but is still able to insert the desired gene into the plant cell.
• It contains vir or virulence genes, which transfer the T-DNA region to plant cells and get integrated into the plant genome.
• Ti plasmid can be modified as per the requirement to insert the desired genes.
• Agrobacterium tumefaciens is called “nature’s genetic engineer”.

Statement 3 is incorrect: They are not found in eukaryotic cell organelles such as mitochondria or chloroplasts.