10. Chromosome number in any species:
[Chhattisgarh PSC (CGPSC) State Service Preliminary Examination, 2019]
(a) Increases with age
(b) Decreases with age
(c) Is constant
(d) Increases with body weight
Answer: (c) Is constant
Explanation: Each species generally has a characteristic chromosome complement in ordinary diploid body cells. Its count is maintained across generations through meiosis and fertilisation. Chromosome number can differ in gametes or due to genetic abnormalities, but it does not normally rise with age or weight.
9. Regarding genetically modified mustard developed in India, consider:
(1) Its bacterial genes give broad pest resistance.
(2) Its introduced genes enable cross-pollination and hybridisation.
(3) It was developed jointly by IARI and Punjab Agricultural University.
Which statements are correct?
[UPSC Civil Services Preliminary Examination, 2018]
(a) 1 and 3 only
(b) 2 only
(c) 2 and 3 only
(d) 1, 2 and 3
Answer: (b) 2 only
Explanation: The barnase–barstar genetic system helps enable hybrid seed production in mustard. The introduced traits were not designed as general protection against many insect pests, and the project was associated with Delhi University researchers rather than the institutional pairing stated.
8. “Particulate theory of inheritance” was proposed by:
[WBCS Preliminary Examination, 2017]
(a) Charles Darwin
(b) Gregor Johann Mendel
(c) Hermann Muller
(d) T. H. Morgan
Answer: (b) Gregor Johann Mendel
Explanation: Mendel proposed that discrete hereditary factors, rather than permanently blending parental characteristics, pass from one generation to another. His pea-plant results demonstrated that recessive traits can remain hidden in hybrids and reappear later, supporting particulate inheritance.
7. The phenotypic ratio of a Mendelian dihybrid cross is:
[WBCS Preliminary Examination, 2015]
(a) 9 : 3 : 3 : 1
(b) 1 : 1 : 1 : 1
(c) 3 : 4 : 3 : 1
(d) 1 : 2 : 1 : 1
Answer: (a) 9 : 3 : 3 : 1
Explanation: For two independently assorting genes showing complete dominance, selfing AaBb hybrids produces four phenotype classes in the ratio 9:3:3:1. The pattern combines two 3:1 monohybrid ratios and requires sufficient independence between the inheritance of the two traits.
6. Who gave the term “genetics”?
[RPSC Senior Teacher Grade II (Science), 2015]
(a) Mendel
(b) Morgan
(c) Bateson
(d) Boveri
Answer: (c) Bateson
Explanation: British biologist William Bateson popularised the term genetics for the scientific study of heredity and variation. Mendel established the experimental laws of inheritance, whereas Thomas Hunt Morgan contributed important evidence for chromosome linkage and the genetic role of chromosomes.
5. Assertion (A): DNA fingerprinting can help establish paternity and identify suspects in criminal investigations.
Reason (R): Small biological samples such as hair, dried blood and semen can provide adequate DNA for analysis.
[Rajasthan RAS Preliminary Examination, 2013]
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (a) Both A and R are true, and R explains A.
Explanation: DNA profiling compares highly variable genetic markers between biological samples and reference individuals. Properly collected samples containing suitable cells can establish identity or biological relationships with statistical support. Thus, the availability of DNA from trace material explains the technique’s forensic usefulness.
4. Knowing the relative positions of genes on a chromosome can help:
(1) identify livestock pedigrees,
(2) understand the causes of all human diseases,
(3) develop disease-resistant animal breeds.
Which are correct?
[UPSC Civil Services Preliminary Examination, 2011]
(a) 1 and 2 only
(b) 2 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c) 1 and 3 only
Explanation: Gene maps help trace inherited markers through pedigrees and select desirable traits, including disease resistance, in animal breeding. However, not every human disease is caused solely by identifiable genetic factors; environmental and infectious causes also contribute. Therefore, the second claim is too broad.
3. Genetics deals with:
[BPSC Preliminary Examination (53rd–55th), 2011]
(a) Mendel’s laws only
(b) Organic evolution only
(c) DNA structure only
(d) Heredity and variations
Answer: (d) Heredity and variations
Explanation: Genetics encompasses how traits pass between generations and why genetically related organisms differ. Its scope includes molecular DNA structure, Mendelian laws, chromosomal inheritance and variation. None of the narrower alternatives captures the entire field, making heredity and variation the comprehensive description.
2. Genome mapping relates to:
[UPPSC Preliminary Examination, 2002]
(a) Blood grouping
(b) Mapping of genes
(c) Mapping of nerve centres
(d) Mapping of the brain
Answer: (b) Mapping of genes
Explanation: Genome mapping determines where genes and molecular markers lie along chromosomes and estimates their order or physical distances. It supports research on inherited disorders, genetic linkage and plant or animal breeding. It is not a map of cerebral or nerve structures.
1. When one gene controls two or more different characters simultaneously, the phenomenon is called:
[UPSC Civil Services Preliminary Examination, 2002]
(a) Apomixis
(b) Pleiotropy
(c) Polyploidy
(d) Polyteny
Answer: (b) Pleiotropy
Explanation: Pleiotropy describes the influence of one gene on multiple phenotypic characteristics. A single mutated gene may therefore affect several tissues or biological functions. Polyploidy involves extra chromosome sets, while apomixis refers to seed production without fertilisation.
