HBSE Class 12 Sample Paper 2026 Answers Biology

BSEH MARKING SCHEME

CLASS- XII Biology (Model Paper 2025-26) Code: A

 The answer points given in the marking scheme are not final.

These are suggestive and indicative. If the examinee has given

different, but appropriate answers, then he should be given

appropriate marks.

Q. Part Answers Marks Total

No. no. Marks

1. --- b) Diploid 1 1

2. --- c) oxytocin 1 1

3. --- b) Green seed 1 1

4. --- d) 0 1 1

5. --- b) AIDS 1 1

6. --- a) curd 1 1

7. --- d) none of these 1 1

8. --- c) Population density 1 1

9. --- a) Energy 1 1

10. --- Ovum and second polar body ½+½ 1

11. --- RNA Polymerase II 1 1

12. --- Inflorescences 1 1

13. --- β-galactosidase 1 1

14. --- Thymidine 1 1

1

BSEH Marking Scheme Class: XII Model Paper (2025-26)

15. --- Temperature and acid/alkali ½+½ 1

16. --- b) Both A and R are true, and R is not the 1 1

correct explanation of A.

17. --- c) A is true but R is false. 1 1

18. --- d) A is false but R is true. 1 1

19. ½ for 2

each

correct

labelling

Or

Hydrilla and Vallisneria ½+½

i) Pollen grains are long and ribbon like ½+½

ii) They have mucilaginous covering

20. Size of genome: 3164.7 million bp ½ 2

Largest gene: dystrophin ½

Chromosome with most gene: 1 ½

Chromosome with least gene: Y ½

21. Homology: thorn and tendrils of 1 2

2
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

Bougainvillea and Cucurbita

Analogy: Sweet potato (root modification) 1

and potato (stem modification)

22. Saccharomyces cerevisiae 1
2
Monascus purpureus 1

23. Polymerase chain reaction (PCR) 1

because it amplifies the target sequence 1

exponentially.

Or
2

1
Enzyme Linked Immune Sorbent Assay test

ELISA is based on the principle of antigen- 1

antibody interaction

24. Somaclones are plants produced by tissue 1

culture that are genetically identical to the

parent plant.
2
Somatic hybrids are hybrid produced by fusion 1

of isolated protoplasts from two different

varieties of plants.

25. a) Commensalism 1

b) Parasitism 1 2

Or

3
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

K = Carrying capacity 1

r = Intrinsic rate of natural increase 1

26. GPP – R = NPP 1

Gross primary productivity of an ecosystem is 1

the rate of production of organic matter per

unit area over a time period by plants during
3
photosynthesis.

Gross primary productivity excluding 1

respiration losses (R), is the net primary

productivity

27. a) Any
biosphere reserves, national parks, wildlife
three,
sanctuaries, sacred groves
½ each 3

b) Zoological parks, botanical gardens, wildlife ½ each

safari parks

28. a) Rhizobium 1

b) Cyanobacteria/ Anabaena/ Nostoc/ Any one

Oscillatoria 1
3
c) Mycorrhiza 1

Or

Methanogens ½

4
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

Methane, Carbon dioxide (CO2), Hydrogen ½+½+

(H2) ½

cooking and lighting ½+½

29. Stabilization: in which more individuals ½+½

acquire mean character value

Directional change: more individuals ½+½

acquire value other than the mean
3
character value

Disruption: more individuals acquire ½+½

peripheral character value at both ends

of the distribution curve

30. z - beta-galactosidase ½+½

y - permease ½+½
3
a - transacetylase ½+½

Or

5
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

1 mark

of

correct

diagram,

½ for

each

correct

label

31. i) Artificial insemination 1

ii) Expensive 1 +1

Required infrastructure and Expertise

Or 4

ICSI: Intra Cytoplasmic Sperm Injection 1+ 1

IUI: Intra Uterine Insemination

iii) GIFT (Gamete Intra-Fallopian Transfer) 1

32. i) Widal Test 1

ii) Typhoid 1

iii) Salmonella typhi 1 4

Or

Yes, antibiotics can kill bacteria ½+½

6
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

iv) 1
Pneumonia

33. a) 3

b) Spermatogonia 1

c) Interstitial cells/ Leydig cells 1 5

Or

3 ½

Seminal vesicles, Two ½+½

Prostate gland, One ½+½

Bulbourethral gland, Two ½+½

½+½+
Fructose, Calcium , Certain enzymes
½

7
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

34. 2

‘Ori’ site: It is essential for replication within ½+½

host cell.
5
R R
Selectable markers (amp & tet ): which ½+½

helps in identifying and eliminating non

transformants and selectively permitting the

growth of the transformants.

Cloning sites (8 sites): In order to link the ½+½

alien DNA, the vector needs to have very few,

preferably single, recognition sites for the

commonly used restriction enzymes.

Or

8
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

3

Impeller for proper mixing with minimum ½

damage

Motor for rotation ½

Sterile air for contamination free environment ½

pH control for optimum conditions ½

35. Aneuploidy ½

a) Down’s syndrome; ½

i) It is due to trisomy of chromosome no. 21 ½

ii) individual is short statured/ 5

small round head, furrowed tongue and ½

partially open mouth

½
b) Klinefelter’s Syndrome;

9
Biology Code: A

BSEH Marking Scheme Class: XII Model Paper (2025-26)

i) It is due to an additional copy of X ½

chromosome (karyotype of 47, XXY).

ii) Gynaecomastia / Such individuals are sterile ½

c) Turner’s Syndrome; ½

i) It is caused due to the absence of one of the ½

X chromosomes, i.e., 45 with X0

ii) Such females are sterile as ovaries are ½

rudimentary

Or

a) Linkage 1

b) Drosophila melanogaster 1

c) i) They could be grown on simple synthetic Any

medium in the laboratory. three,

ii) They complete their life cycle in about two 1 mark

weeks each

iii) a single mating could produce a large

number of progeny flies.

iv) the male and female flies are easily

distinguishable.

v) it has many types of hereditary variations

that can be seen with low power microscopes.

10
Biology Code: A