12th Biology Question in English

Class 12th Board Exam Biology Important Chapter Wise MCQ Question in English


1. Which one of the following is mobile genetic elements ? 

(A) Split gene 

(B) Transposon

(C) Jumping gene

(D) Both (B) and (C) 

Answer :- (B)

2. Lac operon consists of how many structural ganes ? 

(A) 1 (a) 

(B) 2 (y and z)

(C) 3 (z, y and a) 

(D) four 

Answer :- (C)

3. Which among the following anticodon is meant for “GAC” codon of DNA ? 

(A) CTG 


(C) Both A & B 

Answer :- (B)

4. Name the genetic metrial in TMV (Tabacco Mosaic Virus). 

(A) DNA 

(B) RNA single stranded

(C) RNA double stranded


Answer :- (B)

5. Which type of the nitrogenous bases of Purine occur in DNA and RNA ? 

(A) Adenine 

(B) Guranine

(C) Both (A) and (B)

(D) Cytosine

Answer :- (C)

6. Which one is initiation codon? 

(A) UAG and UGA

(B) AUG and GUG

(C) UAA and UAG

(D) UAA and UGA 

Answer :- (B)

7. What will be the base sequence of DNA against the base sequence ‘AUCGCCUGA’ of RNA?





Answer :- (B)

8. The function of polymerase chain reaction is : 

(A) Transcription 

(B) Translation

(C) Both (A) and (B)

(D) DNA amplification 

Answer :- (D)

9. The phenotypic ratio in a dihybrid cross is : 

(A) 3:1 

(B) 1:2:1

(C) 9: 7 

(D) 9:3:3:1

Answer :- (D)

10. Gene for hypertrichosis (having pinna) is present on: 

(A) X-chromosome

(B) Y-chromosome 

(C) Sex chromosome

(D) Autosome

Answer :- (B)

11. A gene pair hides the effect of another gene pair. The phenomenon is : 

(A) Epistasis 

(B) Dominance

(C) Mutation 

(D) None of these

Answer :- (B)

12. In a DNA molecule, the cytosine is 18%. The percentage of adenine is: 

(A) 64

(B) 36 

(C) 82 

(D) 32 

Answer :- (D)

13. Which part of the donor’s eye is used for grafting in order to cure certain cases of blindness ? 

(A) Lens 

(B) Retina

(C) Cornea

(D) Choroid

Answer :- (C)

14. RNA differs from DNA in containing :

(A) phosphate 

(B) ribose

(C) deoxyribose 

(D) cytosine 

Answer :- (B)

15. A sequence of three bases on t RNA which binds to mRNA codon is : 

(A) triplet 

(B) non-sense codon

(C) anticodon 

(D) termination codon 

Answer :- (C)

16. The number of linkage groups in a cell having 2n = 14 is : 

(A) 5

(B) 10 

(C) 7 

(D) 14

Answer :- (C)

17. In which stage does crossing over take place ? 

(A) Leptotene 

(B) Cytokinesis

(C) Pachytene

(D) Diakinesis

Answer :- (C)

18. Nucleic acids are polymers of : 

(A) Nucleotides 

(B) Nucleosides

(C) Amino acids 

(D) Nucleoproteins

Answer :- (A)

19. Pyrimidines present in DNA are : 

(A) Thymine and Cytosine

(B) Adenine and Guanine

(C) Cytosine and Uracil

(D) Thyminie and Uracil 

Answer :- (A)

20. Crossing over takes place in : 

(A) Zygotene 

(B) Leptotene

(C) Pachytene

(D) Metaphase 

Answer :- (C)

21. Which diseases is due to heamoglobin’s defect?

(A) Down’s syndrome

(B) Phenyl ketonuria 

(C) Klinefelter syndrome

(D) Sickle cell anaemia

Answer :- (D)

22. Pyrimidines present in RNA are : 

(A) Cytosine and Thymine

(B) Adenine and Guanine 

(C) Cytosine and Uracil

(D) Thymine and Uracil

Answer :- (C)

23. PCR method is useful for : 

(A) DNA synthesis

(B) Protein synthesis

(C) Amino acid synthesis

(D) DNA amplification 

Answer :- (D)

24. How many codons are present inheritance codon? 

(A) 4

(B) 16 

(C) 32 

(D) 64 

Answer :- (D)

25. Operon model was proposed by : 

(A) Watson and crick

(B) Nirenberg 

(C) Jacob and Monad

(D) none of them

Answer :- (C)

26. DNA and RNA differ by : 

(A) Nitrogen bases and sugars

(B) Nitrogen bases and phosphate groups 

(C) Number of C-atoms in sugars

(D) Sugar and phosphate groups 

Answer :- (A)

27. Who discovered DNA polymerase : 

(A) Okazaki 

(B) Watson and Crick

(C) Meselson and Stahl

(D) Kornberg

Answer :- (D)

28. Khorana was awarded Nobel Prize for : 

(A) Discovering DNA

(B) Discovering RNA 

(C) Chemical synthesis of gene

(D) Discovering DNA polymerase 

Answer :- (C)

29. A gene of operon which forms the repressor protein is: 

(A) Operator 

(B) Promoter

(C) Regulator 

(D) Structural

Answer :- (C)

30. Anticodon found in : 

(A) on DNA 

(B) on tRNA

(C) on rRNA 

(D) on mRNA

Answer :- (B)

31. The coding sequence of a monocistronic structural gene is called : 

(A) Intron 

(B) Exon

(C) Cistron 

(D) Recon 

Answer :- (B)

32. DNA fragments are joined in a correct sequence by : 

(A) DNA ligase 

(B) RNA polymerase

(C) Helicase 

(D) DNA polymerase 

Answer :- (C)

33. Satellite DNA is useful tool in : 

(A) Sex determination

(B) Forensic science

(C) Genetic engineering

(D) Organ Transplantation 

Answer :- (C)

34. The size of the variable number of tandem repeats (VNTR) varies from: 

(A) 0.1 to 20 (kb) 

(B) 20 to 150 (kb)

(C) 100 to 1000 (kb)

(D) 0.001 to 0.1 (kb) 

Answer :- (B)

35. Amplification of gene for interest may be done by : 

(A) MMR 


(C) MRI 

(D) All of these

Answer :- (B)

36. RNAi is used to control pests on which plant ? 

(A) Tobacco 

(B) Mango

(C) Potato 

(D) Poppy 

Answer :- (A)

37. For induction of alien DNA in host cell we may use : 

(A) Gene gun 

(B) Micro-pipette

(C) Both (A) & (B)

(D) None of these

Answer :- (A)

38. Okazaki fragment is : 

(A) RNA (RNA primers)

(B) Small segments of DNA on leading stand 

(C) Small segments of DNA on lagging stand 

(D) None of these 

Answer :- (C)

39. One of these is not prepared directly from DNA: 

(A) m-RNAL

(B) t-RNA

(C) r-RNA 

(D) Protein

Answer :- (D)

40. DNA double helix model was given by : 

(A) Knoll and Ruska

(B) Khorana 

(C) Watson and Crick

(D) Priestley

Answer :- (C)

41. Synthesis of RNA on DNA template is known as: 

(A) Translation 

(B) Trancription 

(C) Transduction 

(D) Replication

Answer :- (B)

42. Uracil is related to: 

(A) RNA 

(B) DNA 

(C) Both (A) and (B)

(D) None of these

Answer :- (A)

43. RNA is the genetic material in : 

(A) prokaryotes

(B) eukaryotes

(C) Tobacco Mosaic Virus (TMV) 

(D) E. coli 

Answer :- (C)

44. Trisomy (2n + 1) causes retardation in child, which is known as : 

(A) Philadelphia 

(B) Down’s Syndrome

(C) Albinism 

(D) None of these

Answer :- (B)

45. DNA fingerprinting is : 

(A) DNA typing 

(B) DNA Profiling

(C) Both ‘A’ and ‘B’

(D) base paring

Answer :- (C)

46. DNA is genetic material of :

(A) T.M.V. 

(B) Bacteriophage

(C) ‘A’ and ‘B’ both

(D) None of these

Answer :- (B)

47. Which of the nitrogenous base is not present in RNA: 

(A) Thymine 

(B) Cytosine

(C) Guarnine 

(D) Adenine

Answer :- (A)

48. Operon Model is representation of :

(A) Gene synthesis 

(B) Gene expression 

(C) Gene regulation

(D) Gene function

Answer :- (D)

49. Which nitrogenous base is absent in DNA ? 

(A) Thymine 

(B) Uracil

(C) Guanine 

(D) Cytosine

Answer :- (B)

50. Formation of m RNA from DNA is called : 

(A) Transcription 

(B) Replication

(C) Translation 

(D) None 

Answer :- (A)

51. Which of the following is involved in transcription of tRNA, 5Sr RNA and Sn RNA of eukaryotes?

(A) RNA polymerase I

(B) RNA polymerase II

(C) RNA polymerase III

(D) All of these

Answer :- (C)

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