CBSE Biology Outside Delhi Past year paper (Set - 1) Solutions - 2015, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – Outside Delhi (Set 1)  
SOLUTION 
 
SECTION A 
 
1. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
2. A cistron is a segment of DNA which codes for a polypeptide.  
 
3. Retroviruses have RNA as genetic material. After the entry of a virus into the body of 
the host, the virus attacks the macrophage cells of the body where the RNA genome of 
the virus replicates to form viral DNA with the help of the reverse transcriptase 
enzyme.      
 
4. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, but the 
cure is not permanent even after infusion of genetically engineered lymphocytes into a 
patient as cells do not always remain alive. 
 
5. Advantages of unleaded petrol in automobiles as fuel: 
(i) Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
(ii) Use of unleaded petrol prevents the release of poisonous gases (e.g. nitrous oxide) 
in the environment. 
 
SECTION B 
 
6. Moss plants produce a large number of male gametes to increase the chances of 
fertilisation, as the eggs are located in the archegonium and the male gametes have to 
swim in water to reach the eggs for fertilisation to occur. The male gametes are called 
antherozoids. 
 
7.  
(a) The combinations with homologous structures are 
(i) Forelimbs of whales and bats 
(ii) Thorns of Bougainvillea and tendrils of Cucurbita 
(b) These homologous structures represent divergent evolution. 
  
Page 2


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – Outside Delhi (Set 1)  
SOLUTION 
 
SECTION A 
 
1. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
2. A cistron is a segment of DNA which codes for a polypeptide.  
 
3. Retroviruses have RNA as genetic material. After the entry of a virus into the body of 
the host, the virus attacks the macrophage cells of the body where the RNA genome of 
the virus replicates to form viral DNA with the help of the reverse transcriptase 
enzyme.      
 
4. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, but the 
cure is not permanent even after infusion of genetically engineered lymphocytes into a 
patient as cells do not always remain alive. 
 
5. Advantages of unleaded petrol in automobiles as fuel: 
(i) Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
(ii) Use of unleaded petrol prevents the release of poisonous gases (e.g. nitrous oxide) 
in the environment. 
 
SECTION B 
 
6. Moss plants produce a large number of male gametes to increase the chances of 
fertilisation, as the eggs are located in the archegonium and the male gametes have to 
swim in water to reach the eggs for fertilisation to occur. The male gametes are called 
antherozoids. 
 
7.  
(a) The combinations with homologous structures are 
(i) Forelimbs of whales and bats 
(ii) Thorns of Bougainvillea and tendrils of Cucurbita 
(b) These homologous structures represent divergent evolution. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
8.    
(a)  Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
(i) A large number of plants can be raised from a single individual plant within a 
relatively short period and in a limited space. 
(ii) Virus-free healthy plants can be produced from the shoot apical meristem. 
 
9. The primary treatment phase of sewage involves the removal of coarse solid materials 
through filtration and sedimentation.  The diluted sewage is passed through a series of 
filters of sequentially small pore sizes to remove large floating objects. Then the filtered 
sewage is passed into the grit chamber where the coarse solid materials settle by 
gravity. After this, the sewage is allowed to pass into a sedimentation tank where the 
suspended materials settle and form the primary sludge. The effluent is then taken for 
the secondary treatment.  
 
10.  Mutualism is the relationship between two organisms where both organisms are 
benefited in terms of food, shelter and substratum for attachment. 
Two examples:  
(i) Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which they are 
associated and obtains, in turn, carbohydrates from the plant. 
(ii) Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
(i) Gene banks: These are the institutes which maintain stocks of viable seeds, live 
growing plants, tissue culture and frozen germplasm with the whole range of 
genetic variability. 
(ii) Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
(iii) Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
(iv) Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture in plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clones are to be maintained. 
 
 
Page 3


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – Outside Delhi (Set 1)  
SOLUTION 
 
SECTION A 
 
1. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
2. A cistron is a segment of DNA which codes for a polypeptide.  
 
3. Retroviruses have RNA as genetic material. After the entry of a virus into the body of 
the host, the virus attacks the macrophage cells of the body where the RNA genome of 
the virus replicates to form viral DNA with the help of the reverse transcriptase 
enzyme.      
 
4. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, but the 
cure is not permanent even after infusion of genetically engineered lymphocytes into a 
patient as cells do not always remain alive. 
 
5. Advantages of unleaded petrol in automobiles as fuel: 
(i) Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
(ii) Use of unleaded petrol prevents the release of poisonous gases (e.g. nitrous oxide) 
in the environment. 
 
SECTION B 
 
6. Moss plants produce a large number of male gametes to increase the chances of 
fertilisation, as the eggs are located in the archegonium and the male gametes have to 
swim in water to reach the eggs for fertilisation to occur. The male gametes are called 
antherozoids. 
 
7.  
(a) The combinations with homologous structures are 
(i) Forelimbs of whales and bats 
(ii) Thorns of Bougainvillea and tendrils of Cucurbita 
(b) These homologous structures represent divergent evolution. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
8.    
(a)  Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
(i) A large number of plants can be raised from a single individual plant within a 
relatively short period and in a limited space. 
(ii) Virus-free healthy plants can be produced from the shoot apical meristem. 
 
9. The primary treatment phase of sewage involves the removal of coarse solid materials 
through filtration and sedimentation.  The diluted sewage is passed through a series of 
filters of sequentially small pore sizes to remove large floating objects. Then the filtered 
sewage is passed into the grit chamber where the coarse solid materials settle by 
gravity. After this, the sewage is allowed to pass into a sedimentation tank where the 
suspended materials settle and form the primary sludge. The effluent is then taken for 
the secondary treatment.  
 
10.  Mutualism is the relationship between two organisms where both organisms are 
benefited in terms of food, shelter and substratum for attachment. 
Two examples:  
(i) Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which they are 
associated and obtains, in turn, carbohydrates from the plant. 
(ii) Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
(i) Gene banks: These are the institutes which maintain stocks of viable seeds, live 
growing plants, tissue culture and frozen germplasm with the whole range of 
genetic variability. 
(ii) Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
(iii) Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
(iv) Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture in plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clones are to be maintained. 
 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
SECTION C 
11.  Apomixis is the mode of reproduction which does not involve formation of zygote 
through gametic fusion.  
Significance of apomixis: 
(i) Adventives embryos are better clones than cuttings. 
(ii) Embryos formed through apomixes are generally free from infections. 
Hybrid varieties provide higher and better yield. If hybrid seeds are produced every 
year, they do not maintain hybrid characters because of segregation of traits. Moreover, 
production of hybrid seeds every year is very costly. This can be avoided by introducing 
apomixes in hybrid seeds. 
 
12.    50% of dominant traits and 50% of recessive traits during a monohybrid cross can be 
obtained by a test cross between a homozygous pea plant and a heterozygous pea plant. 
 
 
 
13.  Satellite DNA are small non-coding but inheritable sequences of bases which can be 
separated as satellite from bulk DNA during density gradient centrifugation. Satellite 
DNA shows polymorphism which forms the basis of DNA fingerprinting. There are short 
nucleotide repeats in the DNA which are specific in each individual and vary in number 
from person to person but are not inherited. These are called ‘variable number tandem 
repeats’ or mini-satellites. Individuals inherit these repeats from their parents which 
are used as genetic markers in a personal identity test. 
  
Page 4


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – Outside Delhi (Set 1)  
SOLUTION 
 
SECTION A 
 
1. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
2. A cistron is a segment of DNA which codes for a polypeptide.  
 
3. Retroviruses have RNA as genetic material. After the entry of a virus into the body of 
the host, the virus attacks the macrophage cells of the body where the RNA genome of 
the virus replicates to form viral DNA with the help of the reverse transcriptase 
enzyme.      
 
4. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, but the 
cure is not permanent even after infusion of genetically engineered lymphocytes into a 
patient as cells do not always remain alive. 
 
5. Advantages of unleaded petrol in automobiles as fuel: 
(i) Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
(ii) Use of unleaded petrol prevents the release of poisonous gases (e.g. nitrous oxide) 
in the environment. 
 
SECTION B 
 
6. Moss plants produce a large number of male gametes to increase the chances of 
fertilisation, as the eggs are located in the archegonium and the male gametes have to 
swim in water to reach the eggs for fertilisation to occur. The male gametes are called 
antherozoids. 
 
7.  
(a) The combinations with homologous structures are 
(i) Forelimbs of whales and bats 
(ii) Thorns of Bougainvillea and tendrils of Cucurbita 
(b) These homologous structures represent divergent evolution. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
8.    
(a)  Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
(i) A large number of plants can be raised from a single individual plant within a 
relatively short period and in a limited space. 
(ii) Virus-free healthy plants can be produced from the shoot apical meristem. 
 
9. The primary treatment phase of sewage involves the removal of coarse solid materials 
through filtration and sedimentation.  The diluted sewage is passed through a series of 
filters of sequentially small pore sizes to remove large floating objects. Then the filtered 
sewage is passed into the grit chamber where the coarse solid materials settle by 
gravity. After this, the sewage is allowed to pass into a sedimentation tank where the 
suspended materials settle and form the primary sludge. The effluent is then taken for 
the secondary treatment.  
 
10.  Mutualism is the relationship between two organisms where both organisms are 
benefited in terms of food, shelter and substratum for attachment. 
Two examples:  
(i) Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which they are 
associated and obtains, in turn, carbohydrates from the plant. 
(ii) Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
(i) Gene banks: These are the institutes which maintain stocks of viable seeds, live 
growing plants, tissue culture and frozen germplasm with the whole range of 
genetic variability. 
(ii) Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
(iii) Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
(iv) Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture in plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clones are to be maintained. 
 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
SECTION C 
11.  Apomixis is the mode of reproduction which does not involve formation of zygote 
through gametic fusion.  
Significance of apomixis: 
(i) Adventives embryos are better clones than cuttings. 
(ii) Embryos formed through apomixes are generally free from infections. 
Hybrid varieties provide higher and better yield. If hybrid seeds are produced every 
year, they do not maintain hybrid characters because of segregation of traits. Moreover, 
production of hybrid seeds every year is very costly. This can be avoided by introducing 
apomixes in hybrid seeds. 
 
12.    50% of dominant traits and 50% of recessive traits during a monohybrid cross can be 
obtained by a test cross between a homozygous pea plant and a heterozygous pea plant. 
 
 
 
13.  Satellite DNA are small non-coding but inheritable sequences of bases which can be 
separated as satellite from bulk DNA during density gradient centrifugation. Satellite 
DNA shows polymorphism which forms the basis of DNA fingerprinting. There are short 
nucleotide repeats in the DNA which are specific in each individual and vary in number 
from person to person but are not inherited. These are called ‘variable number tandem 
repeats’ or mini-satellites. Individuals inherit these repeats from their parents which 
are used as genetic markers in a personal identity test. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
14. The given equation represents the gene frequency of the total population according to 
Hardy–Weinberg law. In this equation, suppose a gene has two alleles A and a, and p is 
the frequency of occurrence of dominant allele A and q is the frequency of occurrence of 
recessive allele a in the parental generation. 
Then according to the equation,  
P
2
 + 2pq + q
2
 = 1 
 where p
2
  = frequency of occurrence of individuals with homozygous dominant alleles 
(AA) 
2pq = frequency of occurrence of heterozygous individuals (Aa) 
q
2
 = frequency of occurrence of individuals with homozygous recessive alleles (aa) 
 
15.    
(a) The doctor injects the preformed antitoxin into the patient’s body. 
(b) The vaccine stimulates the production of antibodies against the antigen for inducing 
active acquired immunity. 
(c) The injection was given to prevent tetanus. It provides acquired immunity. 
 
16. Essentials of good, effective dairy farm management practices are 
(i) Good breeds of dairy farm animals should be selected. 
(ii) Suitable environmental conditions such as adequate ventilation, suitable 
temperature, sufficient light, water, air and well-drained housing accommodation 
should be provided. 
(iii) Each animal should be fed on a balanced ration. 
(iv) Hygiene and proper cleanliness should be included in the housing of animals. 
(v) Animals should be vaccinated at regular time intervals in order to protect them 
from diseases. 
(vi) Regular visits by a veterinary doctor are must. 
 
17.     
Organism Medicinal value Bioactive molecule 
a. Streptococcus  
 
Clot buster for removing 
clots from blood vessels of 
heart attack patients 
Enzyme  
 
 
b. Monascus 
Blood cholesterol lowering 
agents 
Statins 
 
c. Trichoderma 
Immunosuppressant drug Cyclosporine A 
 
       
  
Page 5


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – Outside Delhi (Set 1)  
SOLUTION 
 
SECTION A 
 
1. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
2. A cistron is a segment of DNA which codes for a polypeptide.  
 
3. Retroviruses have RNA as genetic material. After the entry of a virus into the body of 
the host, the virus attacks the macrophage cells of the body where the RNA genome of 
the virus replicates to form viral DNA with the help of the reverse transcriptase 
enzyme.      
 
4. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, but the 
cure is not permanent even after infusion of genetically engineered lymphocytes into a 
patient as cells do not always remain alive. 
 
5. Advantages of unleaded petrol in automobiles as fuel: 
(i) Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
(ii) Use of unleaded petrol prevents the release of poisonous gases (e.g. nitrous oxide) 
in the environment. 
 
SECTION B 
 
6. Moss plants produce a large number of male gametes to increase the chances of 
fertilisation, as the eggs are located in the archegonium and the male gametes have to 
swim in water to reach the eggs for fertilisation to occur. The male gametes are called 
antherozoids. 
 
7.  
(a) The combinations with homologous structures are 
(i) Forelimbs of whales and bats 
(ii) Thorns of Bougainvillea and tendrils of Cucurbita 
(b) These homologous structures represent divergent evolution. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
8.    
(a)  Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
(i) A large number of plants can be raised from a single individual plant within a 
relatively short period and in a limited space. 
(ii) Virus-free healthy plants can be produced from the shoot apical meristem. 
 
9. The primary treatment phase of sewage involves the removal of coarse solid materials 
through filtration and sedimentation.  The diluted sewage is passed through a series of 
filters of sequentially small pore sizes to remove large floating objects. Then the filtered 
sewage is passed into the grit chamber where the coarse solid materials settle by 
gravity. After this, the sewage is allowed to pass into a sedimentation tank where the 
suspended materials settle and form the primary sludge. The effluent is then taken for 
the secondary treatment.  
 
10.  Mutualism is the relationship between two organisms where both organisms are 
benefited in terms of food, shelter and substratum for attachment. 
Two examples:  
(i) Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which they are 
associated and obtains, in turn, carbohydrates from the plant. 
(ii) Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
(i) Gene banks: These are the institutes which maintain stocks of viable seeds, live 
growing plants, tissue culture and frozen germplasm with the whole range of 
genetic variability. 
(ii) Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
(iii) Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
(iv) Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture in plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clones are to be maintained. 
 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
SECTION C 
11.  Apomixis is the mode of reproduction which does not involve formation of zygote 
through gametic fusion.  
Significance of apomixis: 
(i) Adventives embryos are better clones than cuttings. 
(ii) Embryos formed through apomixes are generally free from infections. 
Hybrid varieties provide higher and better yield. If hybrid seeds are produced every 
year, they do not maintain hybrid characters because of segregation of traits. Moreover, 
production of hybrid seeds every year is very costly. This can be avoided by introducing 
apomixes in hybrid seeds. 
 
12.    50% of dominant traits and 50% of recessive traits during a monohybrid cross can be 
obtained by a test cross between a homozygous pea plant and a heterozygous pea plant. 
 
 
 
13.  Satellite DNA are small non-coding but inheritable sequences of bases which can be 
separated as satellite from bulk DNA during density gradient centrifugation. Satellite 
DNA shows polymorphism which forms the basis of DNA fingerprinting. There are short 
nucleotide repeats in the DNA which are specific in each individual and vary in number 
from person to person but are not inherited. These are called ‘variable number tandem 
repeats’ or mini-satellites. Individuals inherit these repeats from their parents which 
are used as genetic markers in a personal identity test. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
14. The given equation represents the gene frequency of the total population according to 
Hardy–Weinberg law. In this equation, suppose a gene has two alleles A and a, and p is 
the frequency of occurrence of dominant allele A and q is the frequency of occurrence of 
recessive allele a in the parental generation. 
Then according to the equation,  
P
2
 + 2pq + q
2
 = 1 
 where p
2
  = frequency of occurrence of individuals with homozygous dominant alleles 
(AA) 
2pq = frequency of occurrence of heterozygous individuals (Aa) 
q
2
 = frequency of occurrence of individuals with homozygous recessive alleles (aa) 
 
15.    
(a) The doctor injects the preformed antitoxin into the patient’s body. 
(b) The vaccine stimulates the production of antibodies against the antigen for inducing 
active acquired immunity. 
(c) The injection was given to prevent tetanus. It provides acquired immunity. 
 
16. Essentials of good, effective dairy farm management practices are 
(i) Good breeds of dairy farm animals should be selected. 
(ii) Suitable environmental conditions such as adequate ventilation, suitable 
temperature, sufficient light, water, air and well-drained housing accommodation 
should be provided. 
(iii) Each animal should be fed on a balanced ration. 
(iv) Hygiene and proper cleanliness should be included in the housing of animals. 
(v) Animals should be vaccinated at regular time intervals in order to protect them 
from diseases. 
(vi) Regular visits by a veterinary doctor are must. 
 
17.     
Organism Medicinal value Bioactive molecule 
a. Streptococcus  
 
Clot buster for removing 
clots from blood vessels of 
heart attack patients 
Enzyme  
 
 
b. Monascus 
Blood cholesterol lowering 
agents 
Statins 
 
c. Trichoderma 
Immunosuppressant drug Cyclosporine A 
 
       
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – Outside Delhi – Set 1 (Solution) 
 
     
OR 
Methanogens are the methane-producing bacteria used during the production of biogas. 
The methanogenic bacteria digest the organic mass to produce marsh gas during the 
secondary treatment of sewage. Marsh gas is a mixture of gases containing methane, 
hydrogen sulphide and carbon dioxide which form biogas. 
 
18.   The correct sequence of the steps involved in biotechnological reaction are 
 
?
?
?
?
?
?
?
Genomic DNA template
Denaturation of ds-DNA
Nucleotides provided
  
Primers
Thermostable DNA polymerase (from )
Enzyme DNA polymerase
Chemically synthesised oligonucleotides
Complement
Thermus aquaticus
?
ary region of DNA
In vitro synthesis of copies of DNA of interest
 
 
19. Potential applications of genetically modified plants: 
(i) GMO crops are more tolerant to abiotic stresses. 
(ii) They have reduced the dependency on chemical pesticides. 
(iii) They have enhanced the nutritional value of food such as vitamin A-enriched rice.