Q671. The bacterium from which Taq polymerase is isolated is:
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.
Showing 671–680 of 1113 questions
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Q672. During the denaturation step of PCR, the temperature is typically raised to approximately:
Explanation
During the denaturation step of a PCR cycle, the reaction mixture is typically heated to a temperature between 94°C and 96°C. This intense heat provides the energy required to break the hydrogen bonds between the complementary nitrogenous bases of the double-stranded DNA template. As a result, the two strands separate completely, providing the necessary single-stranded templates for the primers to bind in the subsequent annealing step.
Q673. What is the primary purpose of the short oligonucleotide primers used in PCR?
Explanation
DNA polymerases cannot initiate the synthesis of a new DNA strand from scratch; they require a pre-existing 3-hydroxyl group to add nucleotides. In PCR, short, synthetic oligonucleotide primers provide this essential starting point. These primers are designed to be complementary to the sequences flanking the target DNA region, ensuring that the polymerase only amplifies the specific segment of interest during the extension phase.
Q674. After 30 cycles of a standard PCR, approximately how many copies of the target DNA are produced from a single double-stranded DNA molecule?
Explanation
PCR is an exponential amplification process. In each cycle, the number of target DNA molecules doubles. The formula for calculating the number of copies is 2 to the power of n, where n is the number of cycles. After thirty cycles, a single starting molecule of DNA is amplified 2 to the power of thirty times, which results in over one billion identical copies.
Q675. Which of the following is not a standard application of PCR?
Explanation
PCR is exclusively a technique for amplifying DNA sequences; it does not involve the cellular machinery necessary for protein synthesis. While PCR can be used to prepare DNA for later protein production in a host cell, the PCR reaction itself does not produce proteins. Standard applications include forensic DNA profiling, medical diagnosis of pathogens, and the study of ancient or degraded DNA from fossils.
Q676. Identify the incorrect statement regarding the annealing step in PCR.
Explanation
The annealing step of PCR does not require DNA ligase. Instead, it relies on the lowering of temperature to allow primers to form hydrogen bonds with their complementary sequences on the single-stranded template. DNA polymerase, not ligase, then extends these primers. Ligase is used in different biotechnological processes to join DNA fragments but is not a component of the standard PCR reaction mixture.
Q677. A thermocycler is an instrument used primarily for:
Explanation
A thermocycler, also known as a PCR machine, is a specialized laboratory instrument designed to automatically cycle through the precise temperature changes required for the denaturation, annealing, and extension steps of the Polymerase Chain Reaction. By accurately and rapidly heating and cooling the reaction tubes, the device allows for the efficient and repeated amplification of DNA sequences without the need for manual intervention.
Q678. Extra-chromosomal, self-replicating, circular, double-stranded DNA molecules found naturally in many bacteria are called:
Explanation
Plasmids are small, circular, double-stranded DNA molecules found in many bacteria, separate from the main chromosomal DNA. They are capable of self-replication and often carry genes that provide a survival advantage, such as antibiotic resistance. Because they are easy to isolate and manipulate, plasmids are the most commonly used vectors in genetic engineering for carrying and cloning foreign DNA segments in host cells.
Q679. Match List-I with List-II regarding cloning vector components:
| Vector Component | Function |
|---|---|
| A. Origin of replication (ori) | i. Region containing several restriction sites for gene insertion |
| B. Selectable marker | ii. Sequence where DNA replication begins |
| C. Multiple cloning site (MCS) | iii. Gene that helps identify transformed cells (e.g., antibiotic resistance) |
| D. Promoter | iv. Sequence needed to initiate transcription of the inserted gene |
Explanation
The origin of replication is where DNA replication begins, a selectable marker identifies transformed cells, the multiple cloning site has several restriction sites for inserting a gene and the promoter starts transcription of the inserted gene. This gives A-ii, B-iii, C-i, D-iv.
Q680. Consider the following statements about gene cloning vectors:
I. pBR322 is a widely used, artificially synthesized plasmid vector.
II. Plasmids can accommodate infinitely large fragments of foreign DNA.
III. Selectable markers allow the differentiation between recombinants and non-recombinants.
Which of the above statement(s) is/are correct?
I. pBR322 is a widely used, artificially synthesized plasmid vector.
II. Plasmids can accommodate infinitely large fragments of foreign DNA.
III. Selectable markers allow the differentiation between recombinants and non-recombinants.
Which of the above statement(s) is/are correct?
Explanation
pBR322 was indeed one of the first widely used artificial plasmid vectors. Selectable markers are essential for distinguishing between host cells that contain the recombinant plasmid and those that do not. However, plasmids have a limited capacity for the size of the foreign DNA they can carry; very large fragments require different vectors like BACs or YACs, making certain statements regarding their capacity incorrect.Answer key for these questions
| Q | Correct answer |
|---|---|
| 671 | (a) Thermus aquaticus |
| 672 | (c) 94-96 C |
| 673 | (b) Provision of a starting point for the polymerase enzyme |
| 674 | (d) Over 1 billion copies |
| 675 | (a) Large-scale protein synthesis within the amplification |
| 676 | (c) It requires the presence of DNA ligase. |
| 677 | (a) Automating the temperature changes required for PCR |
| 678 | (d) Plasmids |
| 679 | (a) A-ii, B-iii, C-i, D-iv |
| 680 | (c) I and III only |
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.