The correct answer is Option (2) -1-b,2-d,3-a,4-c .
| Column 1 |
Column 2 |
| 1) Restriction endonuclease |
b) Hind II |
| 2) Agrobacterium tumifaciens |
d) Tumor inducing (Ti) plasmid |
| 3) Plasmids |
a) Extrachromosomal DNA |
| 4) Bacteriophages |
c) Viruses that infect bacteria |
- Restriction endonuclease - (b) Hind II
Explanation: Restriction enzymes are responsible for cutting DNA at specific locations. They are molecular scissors that recognize specific DNA sequences and cleave the DNA at those sites. This property of restriction enzymes allows scientists to isolate specific DNA fragments and use them in the construction of recombinant DNA molecules. The first restriction endonuclease, Hind II, was isolated and characterized five years later. Hind II was found to always cut DNA molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II.
- Agrobacterium tumefaciens - (d) Tumor inducing (Ti) plasmid
Explanation: Agrobacterium tumefaciens is a pathogenic bacterium that naturally infects several dicot plants. It carries a piece of DNA known as "T-DNA" (transfer DNA) on its tumor-inducing (Ti) plasmid. When this bacterium infects normal plant cells, it transfers the T-DNA into the plant cell's genome. The T-DNA then integrates into the plant's DNA and causes the transformation of normal plant cells into a tumor. The transformed tumor cells produce chemicals required by the pathogen, promoting its growth and providing nutrients to the bacteria. The process of delivering T-DNA into plant cells is an essential step in plant genetic engineering, allowing the introduction of desirable genes into plants for various purposes, such as crop improvement and biotechnology applications.
- Plasmids - (a) Extrachromosomal DNA
Explanation: Plasmids are small, circular pieces of DNA that exist independently of the chromosomal DNA in bacteria. They are considered extrachromosomal DNA because they are not part of the bacterium's chromosomal DNA and often carry genes that confer advantageous traits, such as antibiotic resistance.
- Bacteriophages - (c) Viruses
Explanation: Bacteriophages, or simply phages, are viruses that specifically infect bacteria. They are used in molecular biology as tools to introduce foreign DNA into bacteria for cloning and gene expression studies.
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