This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Ti Plasmids are Transferred from Bacteria to Plants – 1”.
1. How many types of vector systems are used in eukaryotic plants?
Explanation: Three types of vector system have been used with varying degree of success:
i) Vector based on naturally occurring plasmid of Agrobacterium
ii) Direct gene transfer using various types of plasmid DNA
iii) Vectors based on plant viruses.
2. Ti plasmid is the only known plasmid of plant.
Explanation: There is no naturally occurring plasmid known in higher plants. The first known plasmid that is able to express itself in the plant is a bacterial plasmid known as Ti plasmid from the bacterium, Agrobacterium tumefaciens.
3. The Ti is referred to as _____________
a) Translocation inducing
b) Transfer inducing
c) Tumor inducing
d) Translation inducing
Explanation: The Ti of Ti plasmid refers to as tumor inducing plasmid. It is found in the bacterium Agrobacterium tumefaciens which when infects a plant causes tumor.
4. In which of the plant is the crown gall disease caused?
Explanation: The A. tumefaciens causes a crown gall disease in many dicotyledonous plant species. Crown gall occurs when a wound on the stem allow A. tumefaciens bacteria to cause tumor in the crown region of the stem.
5. The size of the Ti plasmid is around ___________
a) Less than 100 kb
b) More than 200 kb
c) Less than 50 kb
d) More than 75 kb
Explanation: The Ti plasmid is a large plasmid that causes the crown gall disease in plants. The size of the Ti plasmid is more than 200 kb in size that contains the genes involved in the infective process.
6. The part of the bacterial plasmid incorporated in the plant genome includes ___________
a) Virulence region
b) T DNA, 25 base pair repeats
c) Entire plasmid
d) Only T-DNA
Explanation: The remarkable feature of Ti plasmid is that, after infection, a part of the molecule is incorporated into the plant genome. This segment of the Ti plasmid is called the T-DNA or transfer DNA.
7. The size of the T-DNA is around ____________
a) 5 – 10 kb
b) 10 – 20 kb
c) 15 – 30 kb
d) 25 – 30 kb
Explanation: The T-DNA contains the genes required for causing the crown gall disease. It is around 15 – 30 kb in length depending upon the strain of the bacterium.
8. The T-DNA contains how many genes for cancer in the plant?
Explanation: The T-DNA contains all the genes that are responsible for the cancerous property in the transformed cells. They are overall 8 in number which resides in the T-DNA that gets incorporated in the plant genome.
9. The sole purpose of the infection of plants by the Ti plasmid is formation of cancer.
Explanation: The formation of cancer is not the sole purpose of infection in the plants. These genes also direct the synthesis of unusual compound called opines, that bacteria use as nutrients.
10. How many process are used to form the chimera Ti plasmid?
Explanation: There are 2 processes that are used to form the chimera Ti plasmid. They are the binary vector strategy and the co-integration strategy.
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