Q71. Identify the incorrect statement regarding DNA ligase.
Genetics, Biotechnology and Nanotechnology: RAS Prelims MCQs
179 RAS Prelims MCQs on genetics, biotechnology and nanotechnology cover DNA structure, chromosomes, recombinant DNA tools, plant tissue culture, biotech products and bioethics. Purines, base pairing, Chargaff’s rule, vectors, totipotency, Humulin, Feynman’s lecture, the Nagoya Protocol and biopiracy are asked as facts and sequences, with explanations that name the process behind each fact.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
Showing 71–80 of 179 questions
Q72. 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.
Q73. 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.
Q74. 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.
Q75. 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.
Q76. The bacterium from which Taq polymerase is isolated is:
Explanation
Taq polymerase is isolated from the bacterium Thermus aquaticus, which was originally discovered in the hot springs of Yellowstone National Park. Because this organism thrives in extremely high-temperature environments, its enzymes have evolved to remain stable and active even at temperatures near boiling. This unique property made it the ideal enzyme for automating the PCR process, which requires repeated heating steps to denature DNA.
Q77. 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.
Q78. 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.
Q79. 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.
Q80. 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.Answer key for these questions
| Q | Correct answer |
|---|---|
| 71 | (d) It can synthesize DNA de novo without a template. |
| 72 | (a) Digestion of invading viral DNA to prevent cell infection |
| 73 | (c) Kary Mullis |
| 74 | (a) B, C, A |
| 75 | (a) Both A and R are true and R is the correct explanation of A. |
| 76 | (a) Thermus aquaticus |
| 77 | (c) 94-96 C |
| 78 | (b) Provision of a starting point for the polymerase enzyme |
| 79 | (d) Over 1 billion copies |
| 80 | (a) Large-scale protein synthesis within the amplification |
Key facts from Genetics, Biotechnology and Nanotechnology
- Adenine is a purine and pairs with thymine through two hydrogen bonds; the distance between consecutive base pairs in B-DNA is 0.34 nm.
- Chargaff’s rule says that adenine equals thymine and guanine equals cytosine; the human karyotype has 22 pairs of autosomes.
- Telomeres maintain genomic stability during DNA replication; heterochromatin is the condensed, inactive region.
- Humulin was the first commercially produced genetically engineered human hormone.
- Totipotency is the capacity of a single plant cell to regenerate a whole plant; the meristem is used to get virus-free plants.
- Richard Feynman’s 1959 lecture began nanotechnology; the Nagoya Protocol governs benefit sharing; the US patent on turmeric was revoked after a biopiracy battle.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Genetics, Biotechnology and Nanotechnology?
This page has 179 practice MCQs on Genetics, Biotechnology and Nanotechnology (Science and Technology). Each has the correct answer, and most have an explanation.
How many hydrogen bonds pair adenine with thymine?
Two. Adenine pairs with thymine by two hydrogen bonds, and guanine pairs with cytosine by three, which is why DNA rich in G and C is more stable.
What is totipotency?
The capacity of a single plant cell to regenerate into an entire plant. It is the basis of plant tissue culture, in which cells grown on a nutrient medium form a callus and then shoots and roots.
Which protocol deals with sharing the benefits of genetic resources?
The Nagoya Protocol to the Convention on Biological Diversity. It ensures that the benefits from using genetic resources are shared fairly with the countries and communities that provide them.