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 21–30 of 179 questions
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q21. Consider the following statements about Mendels laws: I. The law of independent assortment applies to genes located on the same chromosome that are tightly linked. II. A dihybrid cross involves studying two traits simultaneously. III. The law of segregation is universally applicable with no exceptions in diploid organisms. IV. Mendels experiments used Pisum sativum. Which of the above statement(s) is/are correct?
Explanation
Mendels dihybrid crosses involved the simultaneous study of two distinct traits, providing the basis for his laws. The law of segregation is a universal principle in diploid organisms during gamete formation. Mendel used the garden pea, Pisum sativum, for his research. However, the law of independent assortment does not apply to genes located very close together on the same chromosome.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q22. A test cross is performed to determine:
Explanation
A test cross is a genetic tool used to determine whether an organism expressing a dominant trait is homozygous or heterozygous. This is achieved by breeding the individual with a homozygous recessive organism. If any offspring display the recessive phenotype, the parent must be heterozygous. This method is fundamental for verifying the genetic composition of organisms in classical breeding experiments.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q23. Which of the following is the cause of the 9:3:3:1 ratio in a dihybrid cross?
Explanation
The 9:3:3:1 phenotypic ratio in a dihybrid cross is a direct consequence of the Law of Independent Assortment. This principle states that the alleles of two or more different genes get sorted into gametes independently of one another. As a result, the inheritance of one trait does not influence the inheritance of another, leading to diverse combinations in the offspring.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q24. Mendels laws may not apply strictly in which of the following situations?
Explanation
Linked genes are those located close together on the same chromosome. Because they are physically near each other, they tend to be inherited together during meiosis rather than assorting independently. This proximity interferes with the expected Mendelian ratios, such as the 9:3:3:1 dihybrid ratio. Genetic linkage represents a major exception to Mendels original observations regarding the independent assortment of traits.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q25. Identify the incorrect statement regarding Mendelian genetics.
Explanation
When two true-breeding parents with contrasting traits are crossed, the F1 generation typically exhibits a uniform phenotype. In cases of complete dominance, all offspring will display the dominant trait rather than a mix or intermediate phenotype. Recessive traits only reappear in the F2 generation. Other Mendelian principles hold that gametes carry one allele and segregation occurs during the process of meiosis.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q26. If a pea plant with round seeds (RR) is crossed with a plant with wrinkled seeds (rr), what will be the genotype of the F1 generation?
Explanation
In a cross between a homozygous dominant plant (RR) and a homozygous recessive plant (rr), all offspring in the F1 generation will receive one dominant allele and one recessive allele. Therefore, the resulting genotype for all individuals in the F1 generation is Rr. Phenotypically, these plants will all display the dominant round seed trait despite being carriers of the wrinkled seed allele.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q27. Which trait among the following was not studied by Gregor Mendel in pea plants?
Explanation
Gregor Mendel focused his genetic research on seven specific, easily observable traits in the garden pea plant. These included seed shape, seed color, flower color, pod shape, pod color, flower position, and stem height. Root length was not among the characteristics he systematically studied. His careful selection of these clear, binary traits allowed him to derive the fundamental laws of heredity.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q28. Chromosomes that are not involved in sex determination are called:
Explanation
Autosomes are the chromosomes in an organism that are not involved in determining the sex of an individual. In humans, there are twenty-two pairs of autosomes. These chromosomes carry the majority of the genetic information responsible for general bodily functions and physical characteristics. This distinguishes them from the sex chromosomes, or allosomes, which specifically determine the biological sex of the offspring.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q29. In the normal human karyotype, how many pairs of autosomes are present?
Explanation
A normal human karyotype consists of twenty-three pairs of chromosomes, totaling forty-six in each somatic cell. Out of these, twenty-two pairs are classified as autosomes. These pairs are homologous and contain genes for traits unrelated to sex determination. The remaining twenty-third pair consists of the sex chromosomes, which are XX in females and XY in males, completing the full genetic complement.
RAS PrelimsScience and Technology · Genetics, Biotechnology and Nanotechnology
Q30. The highly condensed and transcriptionally inactive region of a chromosome is called:
Explanation
Heterochromatin refers to regions of the chromosome that remain highly condensed and tightly packed throughout the cell cycle. Due to this dense structure, these areas are generally transcriptionally inactive, meaning the genes within them are not expressed. This contrasts with euchromatin, which is less condensed and contains actively transcribed genes. Heterochromatin plays a vital role in maintaining chromosome structural integrity and gene regulation.
Answer key for these questions
Q
Correct answer
21
(b) II, III and IV only
22
(a) Genotype of an individual showing a dominant phenotype
23
(c) Law of Independent Assortment
24
(a) Linked genes on the same chromosome
25
(d) F1 progeny of true-breeding parents show mixed phenotypes
26
(b) Rr
27
(d) Root length
28
(a) Autosomes
29
(a) 22 pairs
30
(b) Heterochromatin
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.
