1. Who developed the chemical techniques to synthesize polynucleotides?
- 1) H. Gobind Khorana
- 2) Fredrick Sanger
- 3) James Watson
- 4) Barbara McClintock
Answer: 1)
Explanation: H. Gobind Khorana developed synthetic techniques to synthesize polynucleotides in the early 1960s as an attempt to decipher the genetic code. Complete bacterial tyrosine t-RNA was transcribed following the aforementioned attempts.
2. Which of the following enzymes in bacteria are responsible for restricting the growth of viruses?
- 1) protease
- 2) topoisomerase
- 3) gyrase
- 4) restriction endonuclease
Answer: 4)
Explanation: The enzymes responsible for restricting the growth of viruses in the bacterial cells. Restriction endonucleases were discovered in 1970s and have been an important tool in recombinant DNA technology ever since.
3. EcoR1 exhibits a two-fold rotational symmetry.
Answer: 2)
Explanation: EcoR1 is a type II restriction endonuclease that exhibits two-fold rotational symmetry. Two-fold rotational symmetry is the conformation where the base sequence can be rotated 180° without any change.
4. Which enzyme is used to join together two different types of DNA molecules?
- 1) protease
- 2) exonuclease
- 3) endonuclease
- 4) ligase
Answer: 4)
Explanation: DNA ligase is used to join two different types of DNA molecules, thus giving rise to a recombinant molecule that can be cloned inside a suitable host to facilitate the gene expression.
5. The first recombinant DNA molecule was synthesized in the year _______
- 1) 1992
- 2) 1982
- 3) 1972
- 4) 1962
Answer: 3)
Explanation: The first recombinant DNA molecule was synthesized in the year 1972 by Paul Berg, Herbert Boyer, Annie Chang, and Stanley Cohen of Stanford University and the University of California, San Francisco.
6. Which observation was made by Avery, Macleod, and McCarty?
- 1) DNA is more stable than RNA
- 2) DNA can denature at high temperatures
- 3) DNA can be taken up from medium
- 4) DNA is a duplex molecule
Answer: 3)
Explanation: According to the experiments performed by Avery, Macleod, and McCarty; it came to be known that bacterial cells can take up the DNA present in the medium. This formed the basis of cloning plasmids in the bacterial cells.
7. Recombinant plasmids are added to a bacterial culture that has been pretreated with ________ ions.
- 1) ferric
- 2) calcium
- 3) magnesium
- 4) iodine
Answer: 2)
Explanation: Recombinant plasmids are added to a bacterial cell culture that is competent for taking up the plasmids from the medium. A culture can be made competent by treatment with calcium ions.
