Q1. Which of the following nitrogenous bases is a purine found in the DNA double helix?
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.
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Q2. In the Watson-Crick model of DNA, how many hydrogen bonds pair Adenine with Thymine?
Explanation
The Watson-Crick model describes the specific base-pairing rules that stabilize the double helix structure. In this molecular arrangement, adenine forms exactly two hydrogen bonds with thymine to ensure complementary pairing. This specific interaction maintains the uniform width of the DNA molecule while allowing for the efficient storage and replication of genetic information during cellular division processes.
Q3. What is the fundamental structural unit of a DNA molecule?
Explanation
A nucleotide serves as the primary structural building block of the deoxyribonucleic acid molecule. Each individual unit consists of three distinct components: a pentose sugar called deoxyribose, a phosphate group, and one of four nitrogenous bases. These units link together via phosphodiester bonds to form long polynucleotide chains, which encode the genetic instructions necessary for life.
Q4. Consider the following statements regarding the DNA double helix:
I. The two strands run in an antiparallel direction.
II. The backbone is constituted by sugar-phosphate.
III. The pitch of the helix is 3.4 nanometers.
Which of the above statements are correct?
I. The two strands run in an antiparallel direction.
II. The backbone is constituted by sugar-phosphate.
III. The pitch of the helix is 3.4 nanometers.
Which of the above statements are correct?
Explanation
The B-form DNA double helix exhibits several defining structural characteristics essential for its biological function. The two strands run in opposite directions, known as an antiparallel orientation. The external backbone is composed of repeating deoxyribose sugar and phosphate units. Furthermore, the helix completes one full turn every 3.4 nanometers, accommodating approximately ten base pairs per turn.
Q5. Given below are two statements, one labeled as
Assertion (A) and the other as Reason (R):
Assertion (A): The two strands of DNA can be separated by heating.
Reason (R): The strands of DNA are held together by weak hydrogen bonds between the nitrogenous bases.
Select the correct answer from the codes given below:
Assertion (A) and the other as Reason (R):
Assertion (A): The two strands of DNA can be separated by heating.
Reason (R): The strands of DNA are held together by weak hydrogen bonds between the nitrogenous bases.
Select the correct answer from the codes given below:
Explanation
Heating DNA provides thermal energy that disrupts the weak hydrogen bonds holding the two complementary strands together. Because these bonds are non-covalent, they break more easily than the covalent phosphodiester backbone when exposed to high temperatures. This separation process, known as denaturation, is fundamental for molecular techniques like polymerase chain reactions and occurs naturally during DNA replication.
Q6. Which among the following is not a function of DNA?
Explanation
DNA primarily functions as the carrier of genetic information and provides the instructions for synthesizing proteins through transcription and translation. While it controls cellular activities and replicates during division, it does not directly synthesize lipids. Lipid synthesis occurs in the cytoplasm, specifically within the smooth endoplasmic reticulum, mediated by various enzymes rather than direct DNA template instructions.
Q7. The distance between two consecutive base pairs in a standard B-DNA double helix is approximately:
Explanation
In the standard B-DNA double helix model, the vertical distance between two adjacent nitrogenous base pairs is approximately 0.34 nanometers. This precise spacing contributes to the overall stability of the helix through base-stacking interactions. Given that one full helical turn covers 3.4 nanometers and contains ten base pairs, the calculated distance between individual steps remains remarkably consistent.
Q8. Which of the following rules states that the amount of adenine equals the amount of thymine, and the amount of guanine equals cytosine in DNA?
Explanation
Erwin Chargaff formulated the rule stating that in the DNA of any given species, the ratio of adenine to thymine is equal, as is the ratio of guanine to cytosine. This observation provided critical evidence for the base-pairing mechanism in the double helix model. These stoichiometric equalities ensure that the total purine content always equals the total pyrimidine content.
Q9. The process by which DNA makes a copy of itself is known as:
Explanation
Replication is the biological process by which a cell creates an identical duplicate of its entire DNA molecule. This occurs during the S-phase of the cell cycle to ensure that both resulting daughter cells receive a complete set of genetic instructions. The process is semi-conservative, meaning each new double helix consists of one original strand and one newly synthesized strand.
Q10. A gene is best defined as:
Explanation
A gene represents the basic physical and functional unit of heredity. Structurally, it is a specific sequence of nucleotides located at a particular position on a chromosome. These segments contain the coded instructions required to synthesize functional products, such as polypeptide chains or various types of RNA molecules, which ultimately determine the traits and characteristics of a living organism.Answer key for these questions
| Q | Correct answer |
|---|---|
| 1 | (b) Adenine |
| 2 | (b) Two |
| 3 | (c) Nucleotide |
| 4 | (d) I, II and III |
| 5 | (a) Both A and R are true and R is the correct explanation of A. |
| 6 | (b) Direct synthesis of lipids in the cytoplasm |
| 7 | (a) 0.34 nm |
| 8 | (a) Chargaffs Rule |
| 9 | (a) Replication |
| 10 | (d) A specific DNA segment encoding a functional protein or RNA |
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.