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Directional Academy
1
Class 12 Biology Solved Paper
Time: 3 Hours
Total Marks: 70
General Instructions:
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1
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2
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Section A contains 5
questions of one mark each, Section B is of 5 questions of two marks each, Section C
is of 12 questions of three marks each, Section D is of 1 question of four marks and
Section E is of 3 questions of five marks each
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There is no overall choice
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A student has to attempt only one of the alternatives in such questions
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Wherever necessary, the diagrams drawn should be neat and properly labelled
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What is the main function of gel electrophoresis?
[1]
3
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Name two lymphoid organs
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Why is Gambusia introduced into drains and ponds?
[1]
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1
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In a cross between a black and a white guinea pig, all F1 members are black
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[2]
(a) What are the possible genotypes at each level?
(b) What will the offspring be like if two F2 whites are mated?
8
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If tall and red flower (heterozygous) for both
characters is crossed with dwarf and white flower, then what will be the
probability of the offspring?
[2]
9
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[2]
Mention any two symptoms of AIDS
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Name two commonly used bioreactors
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[2]
Section C
11
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What is ovulation? What happens to the Graafian follicles after ovulation?
[3]
13
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On selfing, these plants produced
470 plants with purple flowers and 162 with white flowers
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What acts as an inducer in lac operon? How does it switch on the operon?
15
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[3]
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(a) Is this representation indicating a normal human or a sufferer from a certain
related genetic disease? Give reason in support of your answer
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Name the pathogen, vector and symptoms of the disease Elephantiasis (Filariasis)
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(a) Explain how to overcome inbreeding depression in cattle
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(c) Name an improved breed of cattle
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How are red algae more successful to live in deep water?
[3]
20
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Do eukaryotic cells have restriction endonucleases? Justify you answer
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What are the effects of noise pollution?
[3]
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Give an example of the first
successful attempt made towards correction of such diseases
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Anand, a 14-year-old boy, thinks smoking makes him more energetic and feels like
an adult and thus a more responsible citizen
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As a friend, you have to educate him on
[4]
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(a) Why he feels more energetic while smoking
(b) The effects of CO in smoke
(c) Other ill effects on the body
(d) What values are reflected here?
Section E
24
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S
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[5]
OR
What are the major functions of male accessory ducts and glands?
25
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[5]
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OR
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Write the full names of the different types of RNA
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26
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Explain the simplified model of the
carbon cycle in nature
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Ans
Banana is an underground modified stem (rhizome)
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It is recognised by its well-marked nodes and internodes
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2
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3
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It
is self-replicating and carries the genes for sex factor or fertility factor
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Ans
Spleen and tonsils
Dir
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So, it is introduced into drains
and ponds
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Ans
Syngamy is the fusion of male and female gametes
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The term syngamy means ‘fusion of gametes’ and describes the event which occurs
when two gametes of opposite sexes come close to each other and fuse
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The genotype at the F2
level will be BB, Bb, Bb, bb
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8
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Tall and Red × Dwarf and White
Genes
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TR, Tr, tR, tr × tr
These gametes fuse as follows:
Tr
Ttrr
(Tall plant
with white
flowers)
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TR
TtRr
(Tall plant with
red flowers)
tR
ttRr
(Dwarf plant
with red
flowers)
tr
Ttrr
(Dwarf plant
with white
flowers)
Result: 1:1:1:1
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It generates heat which
results in fever
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OR
Symptoms of AIDS:
(i) Swollen lymph nodes and fever
(ii) Sweating at night and weight loss
10
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The importance of using bioreactors is
(i) It provides large volume for cultures
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(ii) It also provides the optimal conditions for achieving the growth of the desired
product such as temperature, pH, vitamins and oxygen
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Ans
Significance of parthenogenesis:
(i) It helps in determining the sex of an animal as in honey bee
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(iii) It rapidly increases the number of animals in a population
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Ans
Ovulation: It is the process of release of the mature ovum from the ovary in the
abdominal cavity
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The corpus luteum secretes progesterone
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If there is no fertilisation, then the corpus
luteum undergoes degeneration and progesterone secretion declines leading to a
fresh start of the menstruation cycle
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Ans
In the F1 generation, only plants producing purple flowers appeared
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In
the F2 generation, purple and white-coloured flowers were produced in the ratio of
3:1
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This occurs because of the segregation of genes during gamete formation
...
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14
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The inducer lactose binds to the
repressor and forms a complex which remains unable to bind to the operator
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This initiates the transcription of the structural genes,
producing the three polypeptides (enzymes)
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15
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(b) In a person who exhibits sickle cell trait, the defect is caused by the substitution
of glutamic acid (Glu) by valine (Val) at the sixth position of the β-chain of
haemoglobin
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It is an autosomal disease and sickle-shaped RBCs will cause
equal deficiency of oxygen in both males and females
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Ans
Pathogen: Filarial worm (Wuchereria bancrofti)
Vector: Culex sp
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(ii) Pathogen blocks the lymphatic system and lymph accumulates in other parts of
the body, resulting in enlargement of these parts of the body
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It is a strong analgesic and has a
sedative and calming effect
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(ii) Cocaine: It is obtained from the coca plant (Erythroxylum coca)
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It has a potent
stimulating action on CNS, producing a sense of euphoria and increased energy
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(iii) Marijuana: It is obtained from the direct inflorescence and the top leaves of the
female plant of Cannabis sativa
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It lowers the levels of sex hormones, suppresses the immune
system and may cause psychosis
...
Ans
(a) The selected animals of the breeding population should be mated with superior
animals of the same breed but unrelated to the breeding population
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(b) Advantages of inbreeding:
(i) It helps in the accumulation of superior genes and the elimination of
undesirable genes
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(iii) It exposes harmful recessive genes for undesirable characters which are
eliminated by selection
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18
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All the
restriction endonucleases have been isolated from the various strains of bacteria,
and they are also named according to the genus and species of prokaryotes
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For example,
EcoRI comes from Escherichia coli RY 13
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Roman numbers following the names indicate the order in which
the enzymes were isolated from that strain of bacteria
...
Ans
Red algae have phycoerythrin, phycocyanin and chlorophyll-a pigments which
make them grow successfully in the deep seas
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Red algae have the capacity to absorb this light
for photosynthesis because of the presence of red pigment (phycoerythrin)
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20
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These
activities is turn have disturbed the food chain and food web of the forest and
have caused soil erosion, floods, droughts and change in physical environment
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The rate of consumption of nonrenewable resources is enhancing with increasing population
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(iii) Because of an increase in population, the number of vehicles and other soundproducing articles (loudspeakers and drums
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Constant exposure to loud noise causes deafness, increase
in nervous tension and blood pressure and heart troubles
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Ans
Effects of noise pollution:
(i) Constant exposure to loud noise causes deafness and increase in nervous
tension and blood pressure
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(iii) It causes emotional disturbances
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Ans
A hereditary disease can be corrected by gene therapy
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The first clinical gene
therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA)
deficiency
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(ii) Lymphocytes are extracted from the patient’s bone marrow and a normal
functional copy of gene coding for ADA is introduced into these lymphocytes
with the help of a retrovirus
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(iv) The lymphocytes produced by these cells contain functional ADA gene and
reactivate the victim’s immune system for life
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Ans
(a) He feels energetic because nicotine raises blood pressure and increases
heartbeat
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(b) CO binds to haemoglobin and reduces the concentration of oxygen
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(d) Values:
(i) Awareness about health
(ii) Consciousness
(iii) Critical thinking
Section E
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(ii) Fruits on maturity become coloured, sweet and flavoured to attract the seeddispersing agents for disposal to distant localities through wind, water and
animals
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(iv) The colours of many young fruits resemble the green leaves and so they are
not easily spotted by animals
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The ducts from the seminal vesicles join the posterior
part of the vas deferens and form the common ejaculatory duct