1. When were the cloning vectors for plants developed?
a) 1900
b) 1980
c) 2000
d) 1910
Explanation: The cloning vectors for plants were first developed in the 1980s and their use has led to the genetically modified crops.
2. Vectors based on naturally occurring ____________ of Agrobacterium are used in plants.
a) Plasmids
b) Phages
c) Cos sites
d) Chromosome
Explanation: Three types of vector systems with varying degrees of success are used in plants. One of them is vectors based on naturally occurring plasmids of Agrobacterium.
3. What is Agrobacterium tumefaciens?
a) Plant species
b) Plant virus
c) Soil microorganism
d) Fertilizer
Explanation: Agrobacterium tumefaciens is a soil micro-organism that causes crown gall disease in many species of dicotyledonous plants.
4. Which disease is caused by Agrobacterium tumefaciens?
a) Crown gall
b) Carcinoma
c) Angiogenesis
d) Fungal infection
Explanation: Crown gall occurs when a wound on the stem allows A. Tumefaciens bacteria to invade the plant. After the infection bacteria causes a cancerous proliferation of the stem tissue in the region of the crown.
5. The ability to cause crown gall disease is associated with the presence of __________ within the bacterial cell.
a) Plasmid
b) Origin
c) Replication sites
d) Polymerase
Explanation: The tumor inducing plasmid present in the bacterial cell of agrobacterium tumefaciens is responsible for causing the crown gall disease
6. What is the size of the Ti plasmid?
a) 10 kb
b) 100 kb
c) 20 kb
d) 200 kb
Explanation: The Ti plasmid is a large plasmid of 200 kb size or greater. It carries numerous genes involved in the infective process.
7. A remarkable feature of the Ti plasmid is that after infection a part of the molecule is integrated into plant chromosomal DNA.
a) true
b) false
Explanation: The part of the Ti plasmid that gets integrated into the plant chromosome after infection is called the T-DNA or the transfer DNA.
8. What is the size range of T-DNA?
a) 15 and 30 kb
b) 5 and 10 kb
c) 50 and 100 kb
d) 1 and 5 kb
Explanation: The size range of T-DNA is between 15 and 30 kb depending upon the strain of bacteria. The whole of this region is integrated into a host chromosome.
9. The T-DNA is maintained in ______ form in the plant.
a) Stable
b) Unstable
c) Integrated
d) Loosely bound
Explanation: The T-DNA after infection and transfer to the host chromosome remains in the plant in a stable form and is passed to the daughter cells after each cell division.
10. What is the special feature of T-DNA?
a) Expression of unusual genes
b) Repression of unusual genes
c) Cell proliferation
d) Cell death
Explanation: The T-DNA contains eight or so genes that are expressed in the plant cell and are responsible for cancerous properties of the transformed cells.