HBSE Class 12 Sample Paper 2027 Biology Marking Scheme

FOR HARYANA CLASS 12 PREPARATION

HBSE Class 12 Sample
Paper 2027 Biology
Marking Scheme
EXAM YEAR TYPE SUBJECT

Haryana Class 12 2027 Answer Key Biology

Notes · Sample Papers · Previous Year Papers · Mock Tests

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BSEH MARKING SCHEME

(Academic)

CLASS- XII Biology (Model Paper 2026-27) Code: A
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 The answer
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s
These emare suggestive and indicative. If the examinee has given gla
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a different, but appropriate answers, then appropriate marks
should be given.

Q. Part Answers Marks Total

No. no. Marks
m
1. --- b) Scutellum
m .co 1 1

2. --- c) Lippes loop s e 1 1
l a
3. --- b) 32 ag 1 1

4. --- a) 200 1 1

5. --- c) Plasmodium 1 1

6. --- c) Trichoderma 1 1

7. --- c) 3
o m1 1
m 8. .c
m .co --- d) None of these
s em 1 1

s e 9. --- c) 3 g la 1 1
g la a
a 10. --- zero 1 1

11. --- Benign/ non-malignant 1 1

12. --- Saccharomyces cerevisiae 1 1

m 1 . c
c. o s e m
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Page 1 of 12

BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

13. --- Ethidium bromide 1 1

14. --- Phytophagous 1 1

15. --- Parasitism in which the parasitic bird lays its 1 1

eggs in the nest of its host and lets the host

incubate them.

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

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

18. --- a) Both A and R are true, and R is the correct 1 1

explanation of A.

19. Gonorrhoea, syphilis, chlamydiasis, genital Any four, 2

warts, trichomoniasis. ½ each

Or

Artificial insemination ½

Used for infertility cases either

i) due to inability of the male partner ½

to inseminate the female

ii) due to very low sperm counts in the ½

ejaculates

In this technique, the semen (collected either ½

from the husband or a healthy donor) is

artificially introduced either into the vagina or

into the uterus
2
Biology Code: A

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Class: XII (Academic) g Model Paper (2026-27)
a BSEH Marking Scheme
a
20. inner cell mass 1 2

These have the potency to give rise to all the 1

tissues and organs.
m
21. Co-dominance
om
½
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em Multiple allelism ½
l as
l as When two different alleles (IA & IB) dominate ag
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together in AB blood group. 2

Or 1

Occurrence of more than two alleles (IA, IB & i)

of a trait in a population.
m
22. National AIDS Control Organisation
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em Tissue
2
Mucus Associated sLymphoid 1
g la
23. a interaction
Antigen-antibody 1

Infection by pathogen can be detected:

by the presence of antigens (proteins, ½

glycoproteins, etc.) m
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2

. c om em
e m las
las a g
by detecting the antibodies synthesised ½

ag against the pathogen.

Or

3
Biology m Code: A . c
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BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

The method of producing thousands of plants 1

through tissue culture is called micro-

propagation.

Even if the plant is infected, the meristem

(apical and axillary) is free of infection. 1

Hence, one can remove the meristem and

grow it in vitro to obtain disease-free plants.

24. Animals that have had their DNA manipulated 1

to possess and express an extra (foreign) gene

are known as transgenic animals.
2
Any two,
Cancer, cystic fibrosis, rheumatoid arthritis and
½ mark
Alzheimer’s.
each

25. Graphical expression of the food or energy 1

relationship between organisms at different

trophic level in an ecosystem.

The pyramid of biomass in sea is generally 1

inverted because the biomass of fishes far 2

exceeds that of phytoplankton.

Or

Productivity ½

Decomposition ½

4
Biology Code: A

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Class: XII (Academic) g Model Paper (2026-27)
a BSEH Marking Scheme
a
Energy flow ½

Nutrient cycling ½

26. hCG (human chorionic gonadotropin); ½
m
corpus luteum
om
½
. co
. c (human placental lactogen);
hPL ½ e m
em l as
3
l as corpus luteum ½ ag
ag
Relaxin; ½

Ovary ½

27. The gene pool (total genes and their alleles) in 1

a population remains a constant. This is called
m
genetic equilibrium.
m .co 3
s e
gene migration or gene flow, genetic drift, Any four,
l a
ag recombination and natural ½ mark
mutation, genetic

selection. each

28. i) They could be grown on simple synthetic

medium in the laboratory. Any

ii) They complete their life cycle in about two m
three,
m c. 1omark
.co weeks.
s em
s em a
iii) a single mating could produce a llarge
g each
3

g la a
a number of progeny flies.

iv) The male and female flies are easily

distinguishable.

5
Biology m Code: A . c
c. o s e m
s em
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BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

v) It has many types of hereditary variations

that can be seen with low power microscopes.

Or

Analysis of traits in a several of generations of 1

a family is called the pedigree analysis.

Autosomal dominant ½

Autosomal recessive ½

X-linked dominant ½

X-linked recessive ½

29. Bacteria like Any one

Rhizobium/Azospirillum/Azotobacter ½

fix atmospheric nitrogen to organic
½
forms.

Fungi form mycorrhiza with plant roots. ½

The fungal part absorbs phosphorus from 3
Any one
soil/ provides resistance to root-borne
½
pathogens/ provides tolerance to salinity

and drought.

Any one
Cyanobacteria like Anabaena/Nostoc/
½
Oscillatoria

6
Biology Code: A

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Class: XII (Academic) g Model Paper (2026-27)
a BSEH Marking Scheme
a
Can fix atmospheric nitrogen in aquatic Any one

and terrestrial environments/ paddy ½

fields/ add organic matter to the soil and
m
increase its fertility
om . co
30. . c
Typhoid ½ e m
e m l as
l as 1 ag
g Salmonella typhi
a
Through contaminated food and water
½

½
Sustained high fever,

Weakness/ stomach pain/ constipation m
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Any one, 3
/headache /loss of appetite
e m
l as ½

ag Or

Erythroxylum coca 1

Datura 1

Atropa belladona m
1
m . o
c 1
c. o 31. i) Hydrogen bonding
s e m
s em ii) Structural Gene
g la 1
l a a
ag Or 4

The DNA strand which is not transcribed is

called coding strand. 1

7
Biology m Code: A . c
c. o s e m
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BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

iii) Prokaryotic Eukaryotic Any two

Transcription Transcription correct

No Splicing is required Splicing is required differences

Single RNA polymerase Three different RNA , 1 mark

is used polymerase are used each
Capping & tailing is not Capping & tailing is

found found

32. i) log 𝑆 = log 𝐶 + Z log 𝐴 2

ii) endemism means that certain species are 1

confined to one region and are not found

anywhere else. 4
iii) 34 1

Or

0.6 – 1.2 1

33. a) Devices used by plants to discourage self- 1

pollination and to encourage cross-

pollination.

Self-incompatibility: 1

This is a genetic mechanism and prevents self- 5

pollen (from the same flower or other flowers

of the same plant) from fertilising the ovules 1

by inhibiting pollen germination or pollen tube

growth in the pistil.
8
Biology Code: A

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Class: XII (Academic) g Model Paper (2026-27)
a BSEH Marking Scheme
a
b) Outbreeding devices promote cross- 1

pollination to avoid inbreeding depression.

c) Dioecy in plants i.e. male and female flowers 1
m
are present on different plants.
om . co
. c Or e m
e m l as
l as
a) 1 mark ag
ag
for

correct

diagram.

½ mark
m
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for each

e m
l as correct

ag label

b) Cells: vegetative cell, generative cell ½+½

Layers: Exine, intine ½+½

34. a) i) transcriptional level (formation of primary ½
transcript)
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ii) processing level (regulation of splicing)
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iii) transport of mRNA from nucleus to a the ½
l a ag
ag cytoplasm

iv) translational level ½

9
Biology m Code: A . c
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BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

b) The repressor protein binds to the operator 1

region of the operon and prevents RNA

polymerase from transcribing the operon.

c) The y gene codes for permease 1

It increases permeability of the cell to β- 1

galactosides.

Or

a) i) It should be able to generate its replica 1

(Replication).

ii) It should be stable chemically and ½

structurally.

iii) It should provide the scope for slow 1

changes (mutation) that are required for

evolution.

iv) It should be able to express itself in the form ½

of 'Mendelian Characters’.

b) i) 2'-OH group present at every nucleotide in 1

RNA is a reactive group and makes RNA labile

and easily degradable.

ii) the presence of thymine at the place of uracil 1

also confers additional stability to DNA.

10
Biology Code: A

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Class: XII (Academic) g Model Paper (2026-27)
a BSEH Marking Scheme
a
35. a) Biotechnology is controlled use of living 1

organisms for human welfare.

or
m
om . co
. c integration of natural science and
The e m
e m l as
l as organisms, cells, parts thereof, and
ag
ag molecular analogues for products and

services.

Genetic engineering: ½

Techniques to alter the chemistry of
m
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½
genetic material (DNA and RNA), to
e m 5
introduce theseas
into host organisms and
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thus changea the phenotype of the host

organism.

Bioprocess engineering: ½

Maintenance of sterile ambience in
o m
m chemical engineering processes to enable . c
m .co s e m ½
s e growth of only the
la
desired
g
g la microbe/eukaryotic cell in
a large
a
quantities.

b) This is a sequence from where replication 1

starts and any piece of DNA when linked to this
11
Biology m Code: A . c
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BSEH Marking Scheme Class: XII (Academic) Model Paper (2026-27)

sequence can be made to replicate within the

host cells.

This sequence is also responsible for 1

controlling the copy number of the linked

DNA.

Or

a) Thermus aquaticus 1

It is sourced for a thermostable DNA ½

polymerase

which remain active during the high
½
temperature induced denaturation of double

stranded DNA in in-vitro amplification of DNA

b) 1 mark

for

correct

diagram.

½ mark

each for

any four

correct

labels

12
Biology Code: A

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