CBSE Class 12 Marking Scheme 2022 for Biology

CLASS XII
BIOLOGY (044)
MARKING SCHEME
TERM 1 (2021-22)

Q.NO. ANSWER MARKS

SECTION- A

1. D. 2 thecae, 4 sporangia 1

2. B. 3,3,2 1
3 in chalazar end 3 in the micropolar end and 2 nuclei in the center.

3. B. Free nuclear endosperm 1

4. A. sporopollenin 1

5. B. ii, iii 1

6. A) (i) and (iv) 1

7. C. blastocyst, Fertilized egg, Unfertilized egg 1

8. B. completion of meiosis II 1

9. C. FSH, estrogen, progesterone 1

10. C. small, White, Small, covered with mucilage 1

11. C. Strawberry 1

12. B. 2 1

13. D. i, ii and iv 1

14. D. Glutamic acid is substituted by Valine in β chain at the sixth 1
position

15. D. Polygenic and quantitative inheritance 1

16. B. Male 16, Female 32 1

17. 1

18. D. (ii) and (iv) 1

19. B. 5′ (upstream) end and 3′ (downstream) end, respectively of the 1
transcription unit

20. B. exons appear but introns do not appear in the mature RNA 1

21. A. lactose is present, and it binds to the repressor 1

22. B. DNase inhibited transformation 1

23. 1

24. A. Probes 1

SECTION - B

25. C. A is true but R is false 1

26. D. A is False but R is true 1

27. C. A is true but R is False. 1

28 C. A is true but R is false 1

29. A. i and ii 1

30. A. antipodal, zygote and endosperm 1

31. A. The flower type which survived is Cleistogamous and it will always 1
exhibit autogamy

32. D. activate smooth muscles 1

33. C. IUT 1

34. B. decrease the movement of the sperms 1

35. C. 500 1

36. D. 60 1
Out of 9:3:3:1 = 16
9+3 will be tall.
Therefore, 12/16 x 80 = 60.

37. C. 2 Red: 2 Pink 1

38. D. Aa x aa 1

39. B. Autosomal recessive 1

40. B. 50% 1

41. B. Ab X Ab 1

42. B. It is a single stranded DNA 1

43. C. 40,000 bp and 13,600 x10-9 m 1

44. B. A is having 2'-OH group which makes it more reactive and 1
structurally unstable whereas B is having 2'-H group which makes it
less reactive and structurally stable

45. D. 0:1:31 1

46. C. (i) Capping (ii) Polyadenylation (iii) mGppp. (iv) Poly(A). 1

47. C. Short non-coding repetitive sequence forming large portion of 1
eukaryotic genome

48. C. Children 1 & 3 1

SECTION - C

49. C. luteinizing hormone 1

50. B. Progesterone 1

51. C. There will be no observed data for Hormone B 1

52. A. Corpus Luteum 1

53. D. 280 days 1

54. B) Subject 2 is pregnant

55. B. ii, iii, iv, v 1

56. C. Affected individual is a female with Down’s syndrome 1

57. D. Deviation from 9:3:3:1 ratio because of linkage of genes 1

58. C. Translation- Elongation 1

59. D. (i)- continuous synthesis , (ii)- discontinuous synthesis (iii) 3’ end 1
(iv) 5’end

60. C: (i) Promotor Site, (ii) Sigma factor (iii) RNA polymerase 1

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Marking Scheme in lieu of diagram based questions for VI candidates
Total Alternative Questions - 20
Section - A

2. C. one meiotic and three mitotic divisions
5. C. nucellus
One meiotic and 3 mitotic divisions.
7. C. Unfertilized egg/ Fertilized egg/ Blastocyst
10. B. water
23. C. i, ii, and iv
Section - B

29. C. secretes oxytocin
39. A. It verifies that DNA is the carrier of genetic information.
44. D. Hydroxyl
48. D. 50% bands similar to father and rest similar to mother

Section – C

A biology student after studying about the different levels of hormones during the menstrual
cycle was comparing 2 subjects (Patients). A table was created after looking at the levels of
hormones A and B for Subject 1 and 2. Read the information in the table and answer the
questions that follow (Q49 to 54):
49. C. Luteinizing Hormone

50. B. Progesterone
51. C. There will be no observed data for Hormone B
52. A. Corpus Luteum
53. D. 280 days
54. B. Subject 2 is pregnant
56. C. Due to failure of cytokinesis after telophase stage of cell division
57. C. Aabb & aaBb
58. C. to the small subunit; on the large subunit.
59. A. DNA polymerase can read only in the direction of 3' to 5'
60. C. When a rho site is reached.

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