CBSE Biology All India Past year paper (solutions) - 2017, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
  
    
 
     
CBSE 
Class XII Biology 
Board Paper 2017 – All India (Set 1)  
SOLUTION 
                                                                                                                           
SECTION A 
 
1. Purple colour of flowers is a dominant phenotype in pea plants. The genotype 
of such plants can be determined by a test cross. 
  
2. Two postulates of Oparin and Haldane with reference to origin of life are 
a) Life originated from pre-existing, non-living organic molecules. 
b) Formation of life was preceded by chemical evolution. 
 
3. The reason for low productivity is inbreeding depression. Mating between 
relatives should not have common ancestors on either side up to four to six 
generations to restore fertility. 
 
4. The gene encoding Cry protein is called cry gene. Cry gene is present in 
Bacillus thuringiensis in which it produces a protein toxin which kills insects. 
 
5. Because of low voltage in the electrostatic precipitator, fine particulates 
which cannot be removed from the electrostatic precipitator may cause 
breathing and respiratory problems. 
 
  
Page 2


  
 
  
    
 
     
CBSE 
Class XII Biology 
Board Paper 2017 – All India (Set 1)  
SOLUTION 
                                                                                                                           
SECTION A 
 
1. Purple colour of flowers is a dominant phenotype in pea plants. The genotype 
of such plants can be determined by a test cross. 
  
2. Two postulates of Oparin and Haldane with reference to origin of life are 
a) Life originated from pre-existing, non-living organic molecules. 
b) Formation of life was preceded by chemical evolution. 
 
3. The reason for low productivity is inbreeding depression. Mating between 
relatives should not have common ancestors on either side up to four to six 
generations to restore fertility. 
 
4. The gene encoding Cry protein is called cry gene. Cry gene is present in 
Bacillus thuringiensis in which it produces a protein toxin which kills insects. 
 
5. Because of low voltage in the electrostatic precipitator, fine particulates 
which cannot be removed from the electrostatic precipitator may cause 
breathing and respiratory problems. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION B 
 
6. In angiosperms, pollen grains are released in the 2-celled stage, whereas in 
other species, the generative cell divides into 2 male gametes and forms the 
3-celled stage.  
During the 2-celled stage, it has two unequal cells—larger vegetative cell and 
smaller generative cell. 
 
7.  
a) When one codon codes for only one amino acid, it is called unambiguous 
genetic code. When the genetic code is valid for all organisms, it is said to 
be universal. 
b) When one amino acid is coded by more than one codon, the code is said 
to be degenerate, whereas the initiator codon represents the START 
codon, i.e. AUG, which initiates the translation process and codes for 
methionine. 
 
8.  
a) Passive immunisation provides quick immune response in the body. 
b) Antihistamines reduce the symptoms of allergy. 
c) Colostrum contains antibodies which protect the infant. 
d) Cytokine barriers work against viral infections which produce an antiviral 
protein, interferon. They protect non-infected cells from further viral 
infection. 
 
9.  
a) Statin: Monascus purpureus 
b) Citric acid: Aspergillus niger 
c) Penicillin: Penicillium notatum 
d) Butyric acid: Clostridium butylicum 
 
10.  
i. CFCs cause ozone depletion which can be prevented. 
ii. Greenhouse effect and global warming will be controlled. 
iii. It is used in making plastics. 
iv. Because of rise in temperature, it will prevent climatic changes. 
OR 
i. Using the cryopreservation technique, sperms, eggs and embryos can be 
stored for a long period in gene banks and seed banks.  
ii. Plants are propagated in vitro using tissue culture methods. 
 
  
Page 3


  
 
  
    
 
     
CBSE 
Class XII Biology 
Board Paper 2017 – All India (Set 1)  
SOLUTION 
                                                                                                                           
SECTION A 
 
1. Purple colour of flowers is a dominant phenotype in pea plants. The genotype 
of such plants can be determined by a test cross. 
  
2. Two postulates of Oparin and Haldane with reference to origin of life are 
a) Life originated from pre-existing, non-living organic molecules. 
b) Formation of life was preceded by chemical evolution. 
 
3. The reason for low productivity is inbreeding depression. Mating between 
relatives should not have common ancestors on either side up to four to six 
generations to restore fertility. 
 
4. The gene encoding Cry protein is called cry gene. Cry gene is present in 
Bacillus thuringiensis in which it produces a protein toxin which kills insects. 
 
5. Because of low voltage in the electrostatic precipitator, fine particulates 
which cannot be removed from the electrostatic precipitator may cause 
breathing and respiratory problems. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION B 
 
6. In angiosperms, pollen grains are released in the 2-celled stage, whereas in 
other species, the generative cell divides into 2 male gametes and forms the 
3-celled stage.  
During the 2-celled stage, it has two unequal cells—larger vegetative cell and 
smaller generative cell. 
 
7.  
a) When one codon codes for only one amino acid, it is called unambiguous 
genetic code. When the genetic code is valid for all organisms, it is said to 
be universal. 
b) When one amino acid is coded by more than one codon, the code is said 
to be degenerate, whereas the initiator codon represents the START 
codon, i.e. AUG, which initiates the translation process and codes for 
methionine. 
 
8.  
a) Passive immunisation provides quick immune response in the body. 
b) Antihistamines reduce the symptoms of allergy. 
c) Colostrum contains antibodies which protect the infant. 
d) Cytokine barriers work against viral infections which produce an antiviral 
protein, interferon. They protect non-infected cells from further viral 
infection. 
 
9.  
a) Statin: Monascus purpureus 
b) Citric acid: Aspergillus niger 
c) Penicillin: Penicillium notatum 
d) Butyric acid: Clostridium butylicum 
 
10.  
i. CFCs cause ozone depletion which can be prevented. 
ii. Greenhouse effect and global warming will be controlled. 
iii. It is used in making plastics. 
iv. Because of rise in temperature, it will prevent climatic changes. 
OR 
i. Using the cryopreservation technique, sperms, eggs and embryos can be 
stored for a long period in gene banks and seed banks.  
ii. Plants are propagated in vitro using tissue culture methods. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION C 
 
11.   
a) It is possible by artificial hybridisation where pollen grain of one flower is 
introduced artificially on the stigma of another flower without self-
incompatibility. 
b)  
 
Pollen tube, after reaching the ovary, enters the ovule. 
12. Haemophilia is a sex-linked trait caused by a recessive gene located in the 
X chromosome. Thalassaemia occurs when there is an abnormality or 
mutation in one of the genes involved in haemoglobin production. 
People with haemophilia have either defective clotting factors or lack 
clotting factors, whereas people with thalassaemia have either abnormal 
haemoglobin or lack haemoglobin in their red blood cells. 
Haemophilia is a sex-linked disorder, but thalassaemia is an autosomal 
disorder. 
 
13.  
a) Two methodologies involved in HGP are expressed sequence tags (EST) 
and sequence annotation. 
EST focuses on identifying all the genes which are expressed as RNA. 
Sequence annotation is the process of marking specific features in a DNA, 
RNA or protein sequence with descriptive information about structure or 
function.  
 
b) YAC stands for yeast artificial chromosome. YAC is used as a host for DNA 
sequencing. 
 
  
Page 4


  
 
  
    
 
     
CBSE 
Class XII Biology 
Board Paper 2017 – All India (Set 1)  
SOLUTION 
                                                                                                                           
SECTION A 
 
1. Purple colour of flowers is a dominant phenotype in pea plants. The genotype 
of such plants can be determined by a test cross. 
  
2. Two postulates of Oparin and Haldane with reference to origin of life are 
a) Life originated from pre-existing, non-living organic molecules. 
b) Formation of life was preceded by chemical evolution. 
 
3. The reason for low productivity is inbreeding depression. Mating between 
relatives should not have common ancestors on either side up to four to six 
generations to restore fertility. 
 
4. The gene encoding Cry protein is called cry gene. Cry gene is present in 
Bacillus thuringiensis in which it produces a protein toxin which kills insects. 
 
5. Because of low voltage in the electrostatic precipitator, fine particulates 
which cannot be removed from the electrostatic precipitator may cause 
breathing and respiratory problems. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION B 
 
6. In angiosperms, pollen grains are released in the 2-celled stage, whereas in 
other species, the generative cell divides into 2 male gametes and forms the 
3-celled stage.  
During the 2-celled stage, it has two unequal cells—larger vegetative cell and 
smaller generative cell. 
 
7.  
a) When one codon codes for only one amino acid, it is called unambiguous 
genetic code. When the genetic code is valid for all organisms, it is said to 
be universal. 
b) When one amino acid is coded by more than one codon, the code is said 
to be degenerate, whereas the initiator codon represents the START 
codon, i.e. AUG, which initiates the translation process and codes for 
methionine. 
 
8.  
a) Passive immunisation provides quick immune response in the body. 
b) Antihistamines reduce the symptoms of allergy. 
c) Colostrum contains antibodies which protect the infant. 
d) Cytokine barriers work against viral infections which produce an antiviral 
protein, interferon. They protect non-infected cells from further viral 
infection. 
 
9.  
a) Statin: Monascus purpureus 
b) Citric acid: Aspergillus niger 
c) Penicillin: Penicillium notatum 
d) Butyric acid: Clostridium butylicum 
 
10.  
i. CFCs cause ozone depletion which can be prevented. 
ii. Greenhouse effect and global warming will be controlled. 
iii. It is used in making plastics. 
iv. Because of rise in temperature, it will prevent climatic changes. 
OR 
i. Using the cryopreservation technique, sperms, eggs and embryos can be 
stored for a long period in gene banks and seed banks.  
ii. Plants are propagated in vitro using tissue culture methods. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION C 
 
11.   
a) It is possible by artificial hybridisation where pollen grain of one flower is 
introduced artificially on the stigma of another flower without self-
incompatibility. 
b)  
 
Pollen tube, after reaching the ovary, enters the ovule. 
12. Haemophilia is a sex-linked trait caused by a recessive gene located in the 
X chromosome. Thalassaemia occurs when there is an abnormality or 
mutation in one of the genes involved in haemoglobin production. 
People with haemophilia have either defective clotting factors or lack 
clotting factors, whereas people with thalassaemia have either abnormal 
haemoglobin or lack haemoglobin in their red blood cells. 
Haemophilia is a sex-linked disorder, but thalassaemia is an autosomal 
disorder. 
 
13.  
a) Two methodologies involved in HGP are expressed sequence tags (EST) 
and sequence annotation. 
EST focuses on identifying all the genes which are expressed as RNA. 
Sequence annotation is the process of marking specific features in a DNA, 
RNA or protein sequence with descriptive information about structure or 
function.  
 
b) YAC stands for yeast artificial chromosome. YAC is used as a host for DNA 
sequencing. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
14.  
 
Ramapithecus Dryopithecus Neanderthal 
1. Had small canines 
and large molars 
2. Walked erect on 
the feet 
1. Muzzles and 
canine large 
2. Arms and legs 
equal sized 
1. Erect posture 
2. Sloping 
forehead and 
flat cranium 
 
15.  
Disease name: Amoebiasis 
Causal organism: Protozoa (Entamoeba histolytica) 
Symptoms: Constipation, abdominal pain, stools with excess mucus 
Vector: Houseflies 
OR 
 
a) Factors such as social pressure, unsupportive family background, curiosity, 
modern lifestyle and pressure to excel in academics compel parents to fear 
about their wards getting trapped in alcohol or drug abuse. 
b) Addiction is a physical or psychological need for a habit-forming substance 
such as a drug or alcohol. 
Dependence is the tendency of the body to manifest a characteristic and 
unpleasant withdrawal syndrome if drugs and alcohol are discontinued. 
 
16.    
a) Desirable characters for sugarcane crop are thick stem, long internodes, 
high sugar content and disease resistance. 
b) The sugarcane variety from South India—Saccharum barberi—was crossed 
with the variety from North India—Saccharum officinarum —to get 
sugarcane varieties combining the desirable qualities of high yield, thick 
stems and high sugar content in plants which grow in North India. 
 
17. Secondary treatment is also called biological treatment because it uses 
organisms—natural organisms and detritus feeders. The process includes 
various steps: 
a) In the activated sludge system, the primary effluent is taken to aeration 
tanks and the liquid is constantly agitated mechanically with pumping of 
air. 
b) A large number of aerobic heterotrophic microbes such as bacteria, fungi, 
yeasts and protozoa grow in the aeration tank and form flocs, which are 
masses of bacteria held together by slime and fungal filaments to form 
mesh-like structures. 
c) The microbes digest organic matter, convert it to microbial biomass and 
release minerals. This reduces the biochemical oxygen demand (BOD). 
Page 5


  
 
  
    
 
     
CBSE 
Class XII Biology 
Board Paper 2017 – All India (Set 1)  
SOLUTION 
                                                                                                                           
SECTION A 
 
1. Purple colour of flowers is a dominant phenotype in pea plants. The genotype 
of such plants can be determined by a test cross. 
  
2. Two postulates of Oparin and Haldane with reference to origin of life are 
a) Life originated from pre-existing, non-living organic molecules. 
b) Formation of life was preceded by chemical evolution. 
 
3. The reason for low productivity is inbreeding depression. Mating between 
relatives should not have common ancestors on either side up to four to six 
generations to restore fertility. 
 
4. The gene encoding Cry protein is called cry gene. Cry gene is present in 
Bacillus thuringiensis in which it produces a protein toxin which kills insects. 
 
5. Because of low voltage in the electrostatic precipitator, fine particulates 
which cannot be removed from the electrostatic precipitator may cause 
breathing and respiratory problems. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION B 
 
6. In angiosperms, pollen grains are released in the 2-celled stage, whereas in 
other species, the generative cell divides into 2 male gametes and forms the 
3-celled stage.  
During the 2-celled stage, it has two unequal cells—larger vegetative cell and 
smaller generative cell. 
 
7.  
a) When one codon codes for only one amino acid, it is called unambiguous 
genetic code. When the genetic code is valid for all organisms, it is said to 
be universal. 
b) When one amino acid is coded by more than one codon, the code is said 
to be degenerate, whereas the initiator codon represents the START 
codon, i.e. AUG, which initiates the translation process and codes for 
methionine. 
 
8.  
a) Passive immunisation provides quick immune response in the body. 
b) Antihistamines reduce the symptoms of allergy. 
c) Colostrum contains antibodies which protect the infant. 
d) Cytokine barriers work against viral infections which produce an antiviral 
protein, interferon. They protect non-infected cells from further viral 
infection. 
 
9.  
a) Statin: Monascus purpureus 
b) Citric acid: Aspergillus niger 
c) Penicillin: Penicillium notatum 
d) Butyric acid: Clostridium butylicum 
 
10.  
i. CFCs cause ozone depletion which can be prevented. 
ii. Greenhouse effect and global warming will be controlled. 
iii. It is used in making plastics. 
iv. Because of rise in temperature, it will prevent climatic changes. 
OR 
i. Using the cryopreservation technique, sperms, eggs and embryos can be 
stored for a long period in gene banks and seed banks.  
ii. Plants are propagated in vitro using tissue culture methods. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
SECTION C 
 
11.   
a) It is possible by artificial hybridisation where pollen grain of one flower is 
introduced artificially on the stigma of another flower without self-
incompatibility. 
b)  
 
Pollen tube, after reaching the ovary, enters the ovule. 
12. Haemophilia is a sex-linked trait caused by a recessive gene located in the 
X chromosome. Thalassaemia occurs when there is an abnormality or 
mutation in one of the genes involved in haemoglobin production. 
People with haemophilia have either defective clotting factors or lack 
clotting factors, whereas people with thalassaemia have either abnormal 
haemoglobin or lack haemoglobin in their red blood cells. 
Haemophilia is a sex-linked disorder, but thalassaemia is an autosomal 
disorder. 
 
13.  
a) Two methodologies involved in HGP are expressed sequence tags (EST) 
and sequence annotation. 
EST focuses on identifying all the genes which are expressed as RNA. 
Sequence annotation is the process of marking specific features in a DNA, 
RNA or protein sequence with descriptive information about structure or 
function.  
 
b) YAC stands for yeast artificial chromosome. YAC is used as a host for DNA 
sequencing. 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
14.  
 
Ramapithecus Dryopithecus Neanderthal 
1. Had small canines 
and large molars 
2. Walked erect on 
the feet 
1. Muzzles and 
canine large 
2. Arms and legs 
equal sized 
1. Erect posture 
2. Sloping 
forehead and 
flat cranium 
 
15.  
Disease name: Amoebiasis 
Causal organism: Protozoa (Entamoeba histolytica) 
Symptoms: Constipation, abdominal pain, stools with excess mucus 
Vector: Houseflies 
OR 
 
a) Factors such as social pressure, unsupportive family background, curiosity, 
modern lifestyle and pressure to excel in academics compel parents to fear 
about their wards getting trapped in alcohol or drug abuse. 
b) Addiction is a physical or psychological need for a habit-forming substance 
such as a drug or alcohol. 
Dependence is the tendency of the body to manifest a characteristic and 
unpleasant withdrawal syndrome if drugs and alcohol are discontinued. 
 
16.    
a) Desirable characters for sugarcane crop are thick stem, long internodes, 
high sugar content and disease resistance. 
b) The sugarcane variety from South India—Saccharum barberi—was crossed 
with the variety from North India—Saccharum officinarum —to get 
sugarcane varieties combining the desirable qualities of high yield, thick 
stems and high sugar content in plants which grow in North India. 
 
17. Secondary treatment is also called biological treatment because it uses 
organisms—natural organisms and detritus feeders. The process includes 
various steps: 
a) In the activated sludge system, the primary effluent is taken to aeration 
tanks and the liquid is constantly agitated mechanically with pumping of 
air. 
b) A large number of aerobic heterotrophic microbes such as bacteria, fungi, 
yeasts and protozoa grow in the aeration tank and form flocs, which are 
masses of bacteria held together by slime and fungal filaments to form 
mesh-like structures. 
c) The microbes digest organic matter, convert it to microbial biomass and 
release minerals. This reduces the biochemical oxygen demand (BOD). 
  
 
CBSE XII  |  Biology 
Board Paper – 2017 – All India – Set 1 (Solution) 
 
     
d) As the BOD of the waste matter is reduced to 10–15% of raw sewage, it 
passes into the settling tank where the bacterial flocs are allowed to 
undergo sedimentation.    
e) The settled material is called activated sludge. 
f) The activated sludge is collected and subjected to anaerobic digestion in a 
separate tank. This tank has oxygen-free atmosphere where anaerobic 
microbes start digesting the bacteria and fungi in the sludge.  
g) Anaerobic microorganisms digest the organic matter into soluble 
substances and gaseous products such as methane, carbon dioxide and 
hydrogen sulphide. Methane is highly inflammable and can be used as 
biogas. 
h) Finally, the treated sewage effluent is subjected to chemical treatment for 
disinfection before releasing it into natural water bodies such as rivers and 
streams. 
 
18.  
a) The palindromic nucleotide sequence serves as recognition sites of DNA by 
which it binds to the site and cuts each of the two strands of the double 
helix at specific points by hydrolysing the phosphodiester backbones. 
b) Restriction endonucleases have the ability to cut the molecules of DNA. 
The restriction enzyme recognises a unique sequence of nucleotides in the 
DNA strand. The complementary DNA strand has the same sequence but in 
the reverse direction, ensuring both strands of DNA are cut at the same 
location. 
 
19.  
a) Role of heat: High temperature (94°C) is maintained during denaturation 
to separate the two strands of DNA. 
b) Role of primers: Primers are small oligonucleotides with varying length of 
10–18 nucleotides and help in the extension of a new chain. 
c) Role of bacterium Thermus aquaticus: Taq DNA Polymerase is a specialised 
thermostable enzyme isolated from the thermophilic bacterium Thermus 
aquaticus which remain active during high temperature-induced 
denaturation of double-stranded DNA. 
 
20. Insulin contains two short polypeptide chains: Chain A and chain B linked 
together by disulphide bridges. Production of insulin by rDNA techniques was 
achieved by the American company Eli Lilly in 1983. It prepared two DNA 
sequences corresponding to A and B chains of human insulin and introduced 
them in plasmids of E. coli for production. The A and B chains produced 
were separated, extracted and combined by creating disulfide bonds to form 
human insulin.