Q661. EcoRI is a widely used restriction enzyme. In its naming convention, what does the co stand for?
Science and Technology: RAS Prelims MCQs
1113 RAS Prelims practice MCQs on science and technology are on this page, in 6 chapters. They cover the basics of everyday science, computers and information technology, defence and space technology in India, genetics, biotechnology and nanotechnology, science and technology policies and government programmes, and recent advances with Indian contributors and indigenisation. Each question has an answer and an explanation.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
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Q662. The specific sequences recognized by restriction endonucleases are typically:
Explanation
Restriction endonucleases typically recognize palindromic sequences in the DNA. A molecular palindrome is a sequence of base pairs that reads the same on both strands when the orientation is kept the same. These symmetrical sequences allow the enzyme, which often functions as a dimer, to bind and cut both strands of the double helix at specific, mirrored locations, enabling precise genetic engineering applications.
Q663. DNA ligase joins two DNA fragments by catalyzing the formation of which type of bond?
Explanation
DNA ligase is the enzyme responsible for permanently joining two DNA fragments by catalyzing the formation of a covalent phosphodiester bond. This bond occurs between the 3-hydroxyl group of one nucleotide and the 5-phosphate group of another. This reaction effectively seals the nicks in the sugar-phosphate backbone of the double helix, resulting in a continuous and stable recombinant DNA molecule for further applications.
Q664. Which of the following is an exception to the rule that restriction endonucleases produce sticky ends?
Explanation
Most commonly used restriction enzymes, such as EcoRI, BamHI, and HindIII, cut the DNA strands at staggered positions within the recognition site, creating short, single-stranded overhanging sticky ends. However, some enzymes like SmaI cut both strands of the DNA at the same central position. This results in blunt ends which do not have overhanging sequences. Blunt-ended fragments are generally more difficult to ligate efficiently.
Q665. Overhanging, single-stranded ends of DNA created by certain restriction enzymes are called:
Explanation
Sticky ends are short, single-stranded overhanging sequences of DNA produced when certain restriction endonucleases cut the double helix in a staggered fashion. These ends are called sticky because they can easily form complementary hydrogen bonds with other DNA fragments cut by the same enzyme. This temporary base-pairing significantly facilitates the subsequent action of DNA ligase, making the cloning process much more efficient and reliable.
Q666. Identify the incorrect statement regarding DNA ligase.
Explanation
DNA ligase is a sealing enzyme that joins existing fragments; it cannot synthesize a new DNA strand from scratch without a template. That function is performed by DNA polymerases.
Q667. The biological role of restriction endonucleases in bacteria is to:
Explanation
In their natural bacterial environment, restriction endonucleases function as a sophisticated defense system against invading viruses known as bacteriophages. When a virus injects its DNA into the bacterium, these enzymes recognize specific sequences in the viral genome and cut it into non-functional pieces. The bacteriums own DNA is protected from this digestion through chemical modifications like methylation, which masks the recognition sites.
Q668. The Polymerase Chain Reaction (PCR) technique was developed by:
Explanation
The Polymerase Chain Reaction technique was developed by Kary Mullis in 1983. This groundbreaking invention revolutionized molecular biology by allowing scientists to amplify specific DNA sequences millions of times in a very short period. For this contribution, Mullis was awarded the Nobel Prize in Chemistry in 1993. PCR is now a standard tool in diagnostics, forensics, and all areas of genetic research worldwide.
Q669. Consider the following steps of the Polymerase Chain Reaction (PCR):
A. Extension
B. Denaturation
C. Annealing
Which of the following represents the correct sequence?
A. Extension
B. Denaturation
C. Annealing
Which of the following represents the correct sequence?
Explanation
A single cycle of the Polymerase Chain Reaction consists of three distinct temperature-dependent steps in a specific order. First is denaturation, where the double-stranded DNA is heated to separate into single strands. Second is annealing, where the temperature is lowered to allow primers to bind to the target. Finally, extension occurs, where the DNA polymerase synthesizes new strands by extending from the primers.
Q670. Given below are two statements, one labeled as
Assertion (A) and the other as Reason (R):
Assertion (A): Taq polymerase is extensively used in the PCR process.
Reason (R): Taq polymerase is a thermostable enzyme that remains active during the high-temperature denaturation step.
Select the correct answer from the codes given below:
Assertion (A) and the other as Reason (R):
Assertion (A): Taq polymerase is extensively used in the PCR process.
Reason (R): Taq polymerase is a thermostable enzyme that remains active during the high-temperature denaturation step.
Select the correct answer from the codes given below:
Explanation
Taq polymerase is indispensable for PCR because it is derived from a thermophilic bacterium and can withstand high temperatures. Standard DNA polymerases would be permanently denatured and inactivated during the 95°C step required to separate DNA strands. The thermostability of Taq allows the enzyme to remain functional throughout multiple cycles of heating and cooling, enabling the automated amplification of the target DNA sequence.Answer key for these questions
| Q | Correct answer |
|---|---|
| 661 | (b) Coli |
| 662 | (c) Palindromic sequences |
| 663 | (d) Phosphodiester bond |
| 664 | (c) SmaI |
| 665 | (b) Sticky ends |
| 666 | (d) It can synthesize DNA de novo without a template. |
| 667 | (a) Digestion of invading viral DNA to prevent cell infection |
| 668 | (c) Kary Mullis |
| 669 | (a) B, C, A |
| 670 | (a) Both A and R are true and R is the correct explanation of A. |
Key facts from Science and Technology
- The RPSC paper is General Knowledge and General Science, so science questions come with a strong dose of applied and recent topics.
- Everyday science questions test the laws and terms of physics, chemistry and biology through examples.
- Defence and space questions pair a missile, satellite or mission with its year and organisation.
- Policy questions ask for the year, the body and the aim of schemes like STIP, the National Quantum Mission and BioE3.
- Health, environment and agriculture are on a separate page, with their own chapters.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Science and Technology?
This page has 1113 practice MCQs on Science and Technology. Each has the correct answer, and most have an explanation.
Which chapters does the science and technology set cover?
Six chapters: basics of everyday science; computers, information and communication technology; defence and space technology in India; genetics, biotechnology and nanotechnology; science and technology policies and government programmes; and recent advances, Indian contributors and indigenisation.
Is science and technology part of the RAS Prelims syllabus?
Yes. The RPSC paper is called General Knowledge and General Science, and its syllabus lists science and technology topics along with environment, health, agriculture and government programmes, so questions can come from any of these areas.
How should I prepare science for RAS Prelims?
Revise the concepts by examples, then learn the missions, schemes and scientists with their year and organisation. Attempt each chapter, read the explanations and keep a list of the facts you missed.