Which one of the following is the correct chronology of invention/ discovery in the field of Bio- technology?
- A.Discovery of Plasmid, Double Helical structure of DNA, DNA fingerprinting, cloning of Dolly
- B.Double Helical structure of DNA, Discovery of Plasmid, DNA fingerprinting, cloning of Dolly
- C.DNA fingerprinting, cloning of Dolly, Double Helical structure of DNA, Discovery of Plasmid
- D.Double Helical structure of DNA, DNA fingerprinting, Discovery of Plasmid, cloning of Dolly
Correct answer
Explanation
The correct answer is A. The order is plasmid (1952), DNA double helix (1953), DNA fingerprinting (1984) and the cloning of Dolly (1996).
Joshua Lederberg coined the word "plasmid" in 1952 for genetic material that lives outside the chromosome; plasmids later became the main vectors of genetic engineering. In 1953 James Watson and Francis Crick proposed the double helix model of DNA, using the X-ray images of Rosalind Franklin and Maurice Wilkins. Alec Jeffreys developed DNA fingerprinting at Leicester in 1984. Dolly the sheep, the first mammal cloned from an adult body cell, was born at the Roslin Institute in Scotland in July 1996, with Ian Wilmut and Keith Campbell leading the work.
B is wrong: it puts the double helix before the plasmid, which came a year earlier.
C is wrong: it runs the sequence almost backwards.
D is wrong: it places the plasmid after DNA fingerprinting, three decades too late.
Exam tip: 1952 plasmid, 1953 double helix, 1984 fingerprinting, 1996 Dolly.
Practice Questions
View allConsider the following animals :
1. Hedgehog
2. Marmot
3. Pangolin
To reduce the chance of being captured by predators, which of the above organisms rolls up/roll up and protects/protect its/their vulnerable parts?
- A.1 and 2
- B.2 only
- C.3 only
- D.1 and 3
Show answer
Hedgehogs and pangolins curl into a tight ball when threatened, covering the soft belly and face with spines or scales; marmots do not.
Read the full explanation →Which one of the following is used in preparing a natural mosquito repellent?
- A.Congress grass
- B.Elephant grass
- C.Lemongrass
- D.Nut grass
Show answer
Lemongrass and its close relative citronella grass yield aromatic oils that keep mosquitoes away, so they are the base of many natural repellents.
Read the full explanation →Which one of the following devices is non-ohmic ?
- A.Conducting copper coil
- B.Electric heating coil
- C.Semi conductor diode
- D.Rheostat
Show answer
A diode does not obey Ohm's law: the current through it is not proportional to the voltage across it. An ohmic conductor gives a straight-line graph of current against voltage, so its resistance stays constant at a fixed temperature.
Read the full explanation →What is the formula mass of anhydrous sodium carbonate? (Given that the atomic masses of sodium, carbon and oxygen are 23 u, 12 u and 16 u respectively)
- A.286 u
- B.106 u
- C.83 u
- D.53 u
Show answer
Anhydrous sodium carbonate is Na₂CO₃, and 2 × 23 + 12 + 3 × 16 = 106 u. Formula mass is the sum of the atomic masses of all the atoms in one formula unit of an ionic compound.
Read the full explanation →Which one of the following minerals is used as a fuel in nuclear power stations ?
- A.Bauxite
- B.Quartz
- C.Feldspar
- D.Pitchblende
Show answer
Pitchblende, or uraninite, is the chief ore of uranium, the fuel used in most nuclear power stations. Pitchblende is a heavy, black mineral made mostly of uranium oxide.
Read the full explanation →