Principles of Inheritance and Variation

37 solved questions from Class 12 Biology, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the primary topic or theoretical principle explored in 'Principles of Inheritance and Variation' (Class 12 BIOLOGY)? medium MCQ Chapter Core Principle
• 2 Which key mechanism or analytical rule is highlighted in 'Principles of Inheritance and Variation'? medium MCQ Key Analytical Mechanism
• 3 What is the primary topic or principle explained in 'Principles of Inheritance and Variation' (Class 12 Biology)? medium MCQ Chapter Core Concept
• 4 Which key observation or fact is central to understanding 'Principles of Inheritance and Variation'? medium MCQ Key Fact & Mechanism
• 5 Why is the study of 'Principles of Inheritance and Variation' important for students of Class 12? medium MCQ Learning Significance
• 6 What is a common application or real-world example related to 'Principles of Inheritance and Variation'? medium MCQ Real World Application
• 7 What key takeaway should students retain after completing 'Principles of Inheritance and Variation'? medium MCQ Chapter Summary & Takeaway
• 8 A monohybrid cross of two heterozygous pea plants (Aa × Aa) is performed. If 2000 seeds are sown, approximately how many will exhibit the dominant phenotype? medium 2 marks Monohybrid segregation ratio
• 9 In a genetic mapping study, the recombination frequency between gene A and gene B is observed to be 12%. Assuming no interference, estimate the map distance between these two loci. Further, explain why this indicates linkage between genes A and B. hard 4 marks Linkage and map distance
• 10 In a population of 2000 individuals, the allele frequency of a recessive allele "r" is 0.4 and the allele frequency of the dominant allele "R" is 0.6. Assuming Hardy–Weinberg equilibrium, how many individuals are expected to be homozygous recessive (rr)? hard 3 marks Hardy–Weinberg equilibrium
• 11 In a pea plant cross, a plant heterozygous for seed colour (Rr) is crossed with a homozygous recessive plant (rr). What proportion of the offspring will have purple seeds? easy MCQ 1 mark Mendelian dominant/recessive inheritance
• 12 An X‑linked recessive disorder (e.g., haemophilia) is present in a carrier female (X^H X^h) who is crossed with a normal male (X^H Y). Determine (i) the genotype and phenotype proportions among male offspring, (ii) the probability that a randomly selected son will be affected, and (iii) explain why daughters are not affected. hard 4 marks Sex‑linked inheritance – X‑linked recessive
• 13 Two genes, C and D, are located on the same chromosome. In a testcross, the recombinant frequency observed between them is 20%. If the observed double‑crossover frequency is 2% while the expected double‑crossover frequency (based on independent recombination of two intervals each 20%) is 4%, what is the coefficient of coincidence and the interference? hard MCQ 3 marks Linkage mapping – coefficient of coincidence & interference
• 14 Which of the following statements correctly describes Mendel's Law of Segregation? easy MCQ 1 mark Law of Segregation
• 15 Consider a dihybrid cross between two heterozygous pea plants for seed shape (R = round, r = wrinkled) and seed colour (Y = yellow, y = green). Both parents have genotype RrYy. Assuming independent assortment, what is the phenotypic ratio of the F1 generation? medium 2 marks Dihybrid cross – independent assortment
• 16 In a population, an X‑linked recessive disease has a prevalence of 1 in 1000 among males. Assuming random mating and Hardy–Weinberg equilibrium, estimate the carrier frequency among females. hard 4 marks X‑linked recessive – prevalence and carrier frequency
• 17 In a population of 5000 individuals, the allele frequency of the dominant allele A is 0.7 and that of recessive allele a is 0.3. Under Hardy–Weinberg equilibrium, how many individuals are expected to be heterozygous (Aa)? hard 4 marks Hardy–Weinberg equilibrium
• 18 Two genes A and B on the same chromosome show a recombination frequency of 30%. The observed double‑crossover frequency is 6%. Calculate the coefficient of coincidence and the interference. medium 3 marks Linkage – recombination frequency
• 19 Two genes, C and D, lie on the same chromosome. In a mapping experiment the recombinant frequency between them is 35 %. The observed double‑crossover frequency is 12 %. What are the coefficient of coincidence and the interference? hard 5 marks Coefficient of coincidence and interference calculation
• 20 In a population of 3000 individuals, allele A has frequency 0.55. Assuming Hardy–Weinberg equilibrium, how many individuals are expected to be heterozygous (Aa)? easy 3 marks Hardy–Weinberg heterozygote calculation
• 21 What is the probability that a seed from the F1 generation of a RrYy × RrYy cross is round and yellow? medium 3 marks Independent assortment probability calculation
• 22 A recessive X‑linked disease has a prevalence of 1 in 2000 among males. Assuming random mating and Hardy–Weinberg equilibrium, what is the carrier frequency among females? medium MCQ 4 marks X‑linked carrier frequency from male prevalence
• 23 In a village of 4000 individuals, the frequency of the recessive allele ‘a’ for a genetic disorder is 0.2. Assuming Hardy–Weinberg equilibrium, calculate the expected number of individuals who are homozygous recessive (aa). medium 3 marks Hardy–Weinberg genotype frequencies
• 24 In Labrador retrievers, coat colour is controlled by two genes. Gene B (B = black, b = brown) is epistatic to gene E (E = pigment production, e = no pigment). Dogs with genotype __ee are white regardless of the B locus. Which of the following phenotypic ratios is expected in the F2 generation from a cross between two heterozygous black Labradors (BbEe × BbEe)? hard MCQ 4 marks Recessive epistasis in coat colour
• 25 Two genes, A and B, are located on the same chromosome. In a testcross, the observed recombination frequency between them is 15 %. (a) Estimate the map distance between A and B in centimorgans. (b) If the double‑crossover frequency observed in a three‑gene testcross (genes A‑B‑C) is 2 % while the expected double‑crossover frequency (based on the individual recombination frequencies of 15 % for A‑B and 20 % for B‑C) is 3 %, calculate (i) the coefficient of coincidence and (ii) the interference. (c) Briefly explain the biological significance of a positive interference value. hard 5 marks Genetic linkage, map distance and interference
• 26 State Mendel’s law of independent assortment and illustrate it with a cross between two heterozygous pea plants for seed shape (Rr) and seed colour (Yy). easy 2 marks Law of independent assortment
• 27 In a dihybrid cross between two heterozygous pea plants for seed shape (Rr) and seed colour (Yy), both parents having genotype RrYy, calculate the probability that a seed from the F1 generation is round and yellow, and the probability that it is round and green. hard 5 marks Independent assortment of two loci
• 28 In a village of 2500 people, the frequency of the recessive allele ‘r’ responsible for a genetic disorder is 0.15. Assuming Hardy–Weinberg equilibrium, how many individuals are expected to be homozygous recessive (rr)? easy 3 marks Hardy–Weinberg population genetics
• 29 Briefly explain the biological significance of a positive interference value in meiosis. easy 2 marks Positive interference in crossing‑over
• 30 In a population of 2000 individuals, the frequency of the dominant allele A (p) is 0.65. Assuming Hardy–Weinberg equilibrium, calculate the expected number of heterozygous individuals (Aa). medium 3 marks Hardy–Weinberg heterozygote frequency
• 31 Which of the following correctly states Mendel’s law of segregation? easy MCQ 1 mark Mendel’s law of segregation
• 32 An X‑linked recessive disorder (e.g., haemophilia) is present in a carrier female (X⁽ʰ⁾X⁽⁺⁾) crossed with a normal male (X⁽⁺⁾Y). State the genotype and phenotype ratios among male offspring, and give the probability that a randomly selected son will be affected. medium 2 marks X‑linked recessive inheritance
• 33 In a three‑gene testcross, the parental genotype is A⁺B⁺C⁺/a b c crossed with a test strain a b c / a b c. The observed recombination frequencies are 12 % between A and B and 18 % between B and C. Among 5000 progeny, 75 double‑crossover individuals are observed. (a) Estimate the map distances (in cM) between A‑B and B‑C. (b) Calculate the coefficient of coincidence and the interference. (c) Propose the most likely gene order. hard 5 marks Genetic linkage mapping and interference
• 34 In a three‑gene testcross, the parental genotype is A^+B^+C^+/abc crossed with a test strain abc/abc. The observed recombination frequencies are 10 % between A and B and 20 % between B and C. Among 4000 progeny, 5 double‑crossover individuals are observed. (a) Estimate the map distances (in cM) between A‑B and B‑C. (b) Calculate the coefficient of coincidence and the interference. (c) Propose the most likely gene order. hard 5 marks Genetic mapping and interference
• 35 A female who carries the allele for haemophilia (X^h X^+) is crossed with a normal male (X^+ Y). Which of the following gives the correct phenotypic ratio of male offspring? easy MCQ 2 marks X‑linked inheritance
• 36 In a dihybrid cross between two heterozygous pea plants for seed shape (Rr) and seed colour (Yy), what is the probability that a seed from the F1 generation is round and green? medium 3 marks Independent assortment
• 37 In a population of 2000 individuals, the allele frequency of the dominant allele A (p) is 0.6. Assuming Hardy–Weinberg equilibrium, how many individuals are expected to be heterozygous (Aa)? medium 3 marks Hardy–Weinberg equilibrium