Biology: CBSE Sample Question Paper- 5 | Sample Papers for Class 12 Medical and Non-Medical PDF Download

 Page 1


d o n e Biology - Sample Paper-4
1) What is the function of fertilization?
Answer:
Fertilization is brought to transmission of genes from both parents to offspring. 
2) What are antigens?
Answer:
Any substance which, when introduced into the body, stimulates the production of antibody, is called antigen.   
3) What are bioreactors?
Answer:
Bioreactors are large vessels (having a volume of 100 to 1000l) in which raw materials are biologically, converted into specific
product by microbes, plant and animal cells or their enzymes.
4) Write the methods to introduce foreign DNA into host cell other than commonly used methods.
Answer:
Microinjection, direct DNA injection and gene gun.                                           
5) What do you mean by global warming?
Answer:
Global warming refers to the increase in the average temperature of the earth. It is caused by the enhanced greenhouse effect
due to the presence of greenhouse gases in higher concentration.  
6) Differentiate between binary fission and budding.
Answer:
Binary fission occurs in unicellular organisms like Amoeba and Paramecium, in which organism divides by cell division to give
two similar and equal organisms. While in budding the organism produces a small outgrowth or bud that grows in size and on
separation from parent forms new individual, e.g.. Hydra and Yeast.      
7)
(i) What is the significance of mutation?
(ii) Certain mutations are called silent mutation. How?
OR
What are linked genes? How can a pair of linked genes be identified?
Answer:
(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though
mutations are random and occur at very slow rates, they are sufficient to create considerable genetic
variations for speciation to occur.
(ii) Silent mutation are those which:
(i) Occur at 3rd base position of codon.
(ii) Do not alter expression of the genes.                                  
OR
The genes present in the same chromosome and staying together during inheritance through generations
without any change are called linked genes. While unlinked genes are found on different
chromosomes.      
A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not
show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio
1 : 1 instead of dihybrid test ratio 1:1:1:1.         
  
Page 2


d o n e Biology - Sample Paper-4
1) What is the function of fertilization?
Answer:
Fertilization is brought to transmission of genes from both parents to offspring. 
2) What are antigens?
Answer:
Any substance which, when introduced into the body, stimulates the production of antibody, is called antigen.   
3) What are bioreactors?
Answer:
Bioreactors are large vessels (having a volume of 100 to 1000l) in which raw materials are biologically, converted into specific
product by microbes, plant and animal cells or their enzymes.
4) Write the methods to introduce foreign DNA into host cell other than commonly used methods.
Answer:
Microinjection, direct DNA injection and gene gun.                                           
5) What do you mean by global warming?
Answer:
Global warming refers to the increase in the average temperature of the earth. It is caused by the enhanced greenhouse effect
due to the presence of greenhouse gases in higher concentration.  
6) Differentiate between binary fission and budding.
Answer:
Binary fission occurs in unicellular organisms like Amoeba and Paramecium, in which organism divides by cell division to give
two similar and equal organisms. While in budding the organism produces a small outgrowth or bud that grows in size and on
separation from parent forms new individual, e.g.. Hydra and Yeast.      
7)
(i) What is the significance of mutation?
(ii) Certain mutations are called silent mutation. How?
OR
What are linked genes? How can a pair of linked genes be identified?
Answer:
(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though
mutations are random and occur at very slow rates, they are sufficient to create considerable genetic
variations for speciation to occur.
(ii) Silent mutation are those which:
(i) Occur at 3rd base position of codon.
(ii) Do not alter expression of the genes.                                  
OR
The genes present in the same chromosome and staying together during inheritance through generations
without any change are called linked genes. While unlinked genes are found on different
chromosomes.      
A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not
show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio
1 : 1 instead of dihybrid test ratio 1:1:1:1.         
  
8) What is genetic difference in between Klinefelter's Syndrome and Turner's Syndrome?
Answer:
Klinefelter's Syndrome is genetic disorder cause due to the presence of an additional copy of X-chromosome resulting into a
karyotype of 47 (44A + XXY) chromosomes. While Turner's Syndrome is caused due to absent of one of the X-chromosome i.e.,
a karyotype of 45 (44A + XO). They are females whereas Klinefelter's are mostly males.
9) What is recombinant DNA technology? List the key tools used in recombinant DNA technology.
Answer:
Recombinant DNA technology, popularly called as genetic engineering, is a stream of biotechnology which deals with the
manipulation of genetic material by man in vitro. The key tools include restriction enzymes, polymerases, ligases, cloning vectors
& competent host organism.  
10) What is meant by ozone shield? How do CFC and ozone deplete substances affect ozone shield?
Answer:
In the stratosphere between 20-26 kms above sea level, there exist an ozone layer, averaging 0.29 cm above equator and exceed
40 cm above poles at end of winter season. This layer protects earth Biota from harmful effect of strong UV radiation and is
called ozone shield.               escape units stratosphere cause and destruction of  layer,
CFC, which produces 'active chlorine' in presence of UV radiation has most damaging effect. These radicals catalytically destroy
ozone of oxygen.  
11) Is it essential to provide sex education to adolescents? Comment.
Answer:
Sex education is essential to adolescents as it will provide right information to the young minds. It will discourage children from
believing in myths and having misconceptions about sex-related aspects. Proper information about reproductive organs, safe
and hygienic sexual practices, sexually transmitted diseases, AIDS, etc., would help those in adolescent age group to lead a
reproductively healthy life. 
12) What is multiple allelism? Explain.
Answer:
More than two alternate forms of gene present on the same locus called multiple alleles. There is absence of crossing over in
multiple alleles and the mode of inheritance in case of multiple alleles is called multiple allelism. The wellknown example of
multiple allele in human is blood group which also shows condominance. Landsteiner discovered the three blood groups in man
(A, B and 0). Multiple alleles express different alternatives of the same characters. 
13) Explain the permanent methods of birth control.
Answer:
Sterilisation provides a permanent birth control. It is called vasectomy in men and tubectomy in women. In vasectomy, a small
part of the vas deferens is removed or tied up through a small incision on the scrotum, whereas in tubectomy, a small part of the
fallopian tube is removed or tied up through a small incision in the abdomen, or through vagina. These techniques are highly
effective but their reversibility is very poor. 
14) Give the reasons for Mendel's success.
Answer:
Mendel succeeded in formulating the principles of heredity due to following reasons:
(i) The choice of garden pea (Pisum sativum) as experiment material for the hybridisation (controlled
breeding) proved to be good aid for his success, as it can be easily cross-pollinated.
(ii) Mendel selected true-breeding (pure) pea plants for his experiments.
Page 3


d o n e Biology - Sample Paper-4
1) What is the function of fertilization?
Answer:
Fertilization is brought to transmission of genes from both parents to offspring. 
2) What are antigens?
Answer:
Any substance which, when introduced into the body, stimulates the production of antibody, is called antigen.   
3) What are bioreactors?
Answer:
Bioreactors are large vessels (having a volume of 100 to 1000l) in which raw materials are biologically, converted into specific
product by microbes, plant and animal cells or their enzymes.
4) Write the methods to introduce foreign DNA into host cell other than commonly used methods.
Answer:
Microinjection, direct DNA injection and gene gun.                                           
5) What do you mean by global warming?
Answer:
Global warming refers to the increase in the average temperature of the earth. It is caused by the enhanced greenhouse effect
due to the presence of greenhouse gases in higher concentration.  
6) Differentiate between binary fission and budding.
Answer:
Binary fission occurs in unicellular organisms like Amoeba and Paramecium, in which organism divides by cell division to give
two similar and equal organisms. While in budding the organism produces a small outgrowth or bud that grows in size and on
separation from parent forms new individual, e.g.. Hydra and Yeast.      
7)
(i) What is the significance of mutation?
(ii) Certain mutations are called silent mutation. How?
OR
What are linked genes? How can a pair of linked genes be identified?
Answer:
(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though
mutations are random and occur at very slow rates, they are sufficient to create considerable genetic
variations for speciation to occur.
(ii) Silent mutation are those which:
(i) Occur at 3rd base position of codon.
(ii) Do not alter expression of the genes.                                  
OR
The genes present in the same chromosome and staying together during inheritance through generations
without any change are called linked genes. While unlinked genes are found on different
chromosomes.      
A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not
show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio
1 : 1 instead of dihybrid test ratio 1:1:1:1.         
  
8) What is genetic difference in between Klinefelter's Syndrome and Turner's Syndrome?
Answer:
Klinefelter's Syndrome is genetic disorder cause due to the presence of an additional copy of X-chromosome resulting into a
karyotype of 47 (44A + XXY) chromosomes. While Turner's Syndrome is caused due to absent of one of the X-chromosome i.e.,
a karyotype of 45 (44A + XO). They are females whereas Klinefelter's are mostly males.
9) What is recombinant DNA technology? List the key tools used in recombinant DNA technology.
Answer:
Recombinant DNA technology, popularly called as genetic engineering, is a stream of biotechnology which deals with the
manipulation of genetic material by man in vitro. The key tools include restriction enzymes, polymerases, ligases, cloning vectors
& competent host organism.  
10) What is meant by ozone shield? How do CFC and ozone deplete substances affect ozone shield?
Answer:
In the stratosphere between 20-26 kms above sea level, there exist an ozone layer, averaging 0.29 cm above equator and exceed
40 cm above poles at end of winter season. This layer protects earth Biota from harmful effect of strong UV radiation and is
called ozone shield.               escape units stratosphere cause and destruction of  layer,
CFC, which produces 'active chlorine' in presence of UV radiation has most damaging effect. These radicals catalytically destroy
ozone of oxygen.  
11) Is it essential to provide sex education to adolescents? Comment.
Answer:
Sex education is essential to adolescents as it will provide right information to the young minds. It will discourage children from
believing in myths and having misconceptions about sex-related aspects. Proper information about reproductive organs, safe
and hygienic sexual practices, sexually transmitted diseases, AIDS, etc., would help those in adolescent age group to lead a
reproductively healthy life. 
12) What is multiple allelism? Explain.
Answer:
More than two alternate forms of gene present on the same locus called multiple alleles. There is absence of crossing over in
multiple alleles and the mode of inheritance in case of multiple alleles is called multiple allelism. The wellknown example of
multiple allele in human is blood group which also shows condominance. Landsteiner discovered the three blood groups in man
(A, B and 0). Multiple alleles express different alternatives of the same characters. 
13) Explain the permanent methods of birth control.
Answer:
Sterilisation provides a permanent birth control. It is called vasectomy in men and tubectomy in women. In vasectomy, a small
part of the vas deferens is removed or tied up through a small incision on the scrotum, whereas in tubectomy, a small part of the
fallopian tube is removed or tied up through a small incision in the abdomen, or through vagina. These techniques are highly
effective but their reversibility is very poor. 
14) Give the reasons for Mendel's success.
Answer:
Mendel succeeded in formulating the principles of heredity due to following reasons:
(i) The choice of garden pea (Pisum sativum) as experiment material for the hybridisation (controlled
breeding) proved to be good aid for his success, as it can be easily cross-pollinated.
(ii) Mendel selected true-breeding (pure) pea plants for his experiments.
(iii) He confined his study with two conditions of a single character at a time. When behaviour of one
character was established than he took two characters together and so on. This simplified the
observation to be made.
(iv) Mendel also kept accurate records of several generations, so that he could trace the ancestry of a
plant back from the beginning of the studies.
(v) The application of statistical methods and use of law of probability for analysing the results of
experiments was another key of Mendel's success.
(vi) Mendel was fortunate enough that the characters which he chosen for the crossing experiments in
garden pea did not show incomplete dominance, linkage to the genes of other characters and genes
interaction.
15) Write in a few lines about Watson and Crick Model of DNA molecule. Give its potential also.
Answer:
The DNA molecule has the form of a twisted ladder (figure). The vertical bars of the ladder are formed by alternating deoxyribose
sugar and phosphate components, while horizontal rings of the ladder are attached to the deoxyribose sugar components of the
vertical bars which are composed ofpurines and pyrimidines linked up through hydrogen bonds. 
16) How do industrial melanism confirms the natural selection theory of Darwinism?
Answer:
The replacement of white coloured moth by dark coloured melanic species due to industrial smoke is called industrial melanism.
It is a very nice example of natural selection in which a normal trait is changed in response to a changing environment to produce
better adapted individuals. This is because during industrialisation, the tree trunks covered by white lichens became dark due to
air pollution (dust and soot particles). Due to this, white-winged moths could be easily eaten by the predators as they failed in
camouflaging-(hide or disguise the pesence of a person, animal or object by means of camouflage).
17) How are biofertilizers different from fertilizers such as NPK that we buy in the market? Justify the role of Rhizobium as a
biofertilizer.
Answer:
NPK fertilizers are chemical fertilizers which are composed ofnitrogen(N), phosphorus(P) and potassium(K). Excessive use of
these chemical fertilizers causes deterioration of soil by destroying natural bacterial population and increased salt content of the
soil. While biofertilizers are organisms that enrich the quality of soil by natural process and do not harm the soil. The bacterium
Rhizobium present in the root nodules of leguminous plants fix atmospheric nitrogen thereby increasing the fertility of soil. Thus,
Rhizobium is a natural biofertilizer.   
18) What is meant by germplasm collection? What are its benefits?
Answer:
The collection of all the diverse alleles of all the genes of a crop plant is called germplasm collection.  It is of great benefits in
plant breeding programmes as it offers, to the breeders, the entire of genes and alleles and the characteristics which they
express. The breeder selects the most favourable characters of a particular gene and manipulates its transfer to a desirable
parent.
Page 4


d o n e Biology - Sample Paper-4
1) What is the function of fertilization?
Answer:
Fertilization is brought to transmission of genes from both parents to offspring. 
2) What are antigens?
Answer:
Any substance which, when introduced into the body, stimulates the production of antibody, is called antigen.   
3) What are bioreactors?
Answer:
Bioreactors are large vessels (having a volume of 100 to 1000l) in which raw materials are biologically, converted into specific
product by microbes, plant and animal cells or their enzymes.
4) Write the methods to introduce foreign DNA into host cell other than commonly used methods.
Answer:
Microinjection, direct DNA injection and gene gun.                                           
5) What do you mean by global warming?
Answer:
Global warming refers to the increase in the average temperature of the earth. It is caused by the enhanced greenhouse effect
due to the presence of greenhouse gases in higher concentration.  
6) Differentiate between binary fission and budding.
Answer:
Binary fission occurs in unicellular organisms like Amoeba and Paramecium, in which organism divides by cell division to give
two similar and equal organisms. While in budding the organism produces a small outgrowth or bud that grows in size and on
separation from parent forms new individual, e.g.. Hydra and Yeast.      
7)
(i) What is the significance of mutation?
(ii) Certain mutations are called silent mutation. How?
OR
What are linked genes? How can a pair of linked genes be identified?
Answer:
(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though
mutations are random and occur at very slow rates, they are sufficient to create considerable genetic
variations for speciation to occur.
(ii) Silent mutation are those which:
(i) Occur at 3rd base position of codon.
(ii) Do not alter expression of the genes.                                  
OR
The genes present in the same chromosome and staying together during inheritance through generations
without any change are called linked genes. While unlinked genes are found on different
chromosomes.      
A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not
show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio
1 : 1 instead of dihybrid test ratio 1:1:1:1.         
  
8) What is genetic difference in between Klinefelter's Syndrome and Turner's Syndrome?
Answer:
Klinefelter's Syndrome is genetic disorder cause due to the presence of an additional copy of X-chromosome resulting into a
karyotype of 47 (44A + XXY) chromosomes. While Turner's Syndrome is caused due to absent of one of the X-chromosome i.e.,
a karyotype of 45 (44A + XO). They are females whereas Klinefelter's are mostly males.
9) What is recombinant DNA technology? List the key tools used in recombinant DNA technology.
Answer:
Recombinant DNA technology, popularly called as genetic engineering, is a stream of biotechnology which deals with the
manipulation of genetic material by man in vitro. The key tools include restriction enzymes, polymerases, ligases, cloning vectors
& competent host organism.  
10) What is meant by ozone shield? How do CFC and ozone deplete substances affect ozone shield?
Answer:
In the stratosphere between 20-26 kms above sea level, there exist an ozone layer, averaging 0.29 cm above equator and exceed
40 cm above poles at end of winter season. This layer protects earth Biota from harmful effect of strong UV radiation and is
called ozone shield.               escape units stratosphere cause and destruction of  layer,
CFC, which produces 'active chlorine' in presence of UV radiation has most damaging effect. These radicals catalytically destroy
ozone of oxygen.  
11) Is it essential to provide sex education to adolescents? Comment.
Answer:
Sex education is essential to adolescents as it will provide right information to the young minds. It will discourage children from
believing in myths and having misconceptions about sex-related aspects. Proper information about reproductive organs, safe
and hygienic sexual practices, sexually transmitted diseases, AIDS, etc., would help those in adolescent age group to lead a
reproductively healthy life. 
12) What is multiple allelism? Explain.
Answer:
More than two alternate forms of gene present on the same locus called multiple alleles. There is absence of crossing over in
multiple alleles and the mode of inheritance in case of multiple alleles is called multiple allelism. The wellknown example of
multiple allele in human is blood group which also shows condominance. Landsteiner discovered the three blood groups in man
(A, B and 0). Multiple alleles express different alternatives of the same characters. 
13) Explain the permanent methods of birth control.
Answer:
Sterilisation provides a permanent birth control. It is called vasectomy in men and tubectomy in women. In vasectomy, a small
part of the vas deferens is removed or tied up through a small incision on the scrotum, whereas in tubectomy, a small part of the
fallopian tube is removed or tied up through a small incision in the abdomen, or through vagina. These techniques are highly
effective but their reversibility is very poor. 
14) Give the reasons for Mendel's success.
Answer:
Mendel succeeded in formulating the principles of heredity due to following reasons:
(i) The choice of garden pea (Pisum sativum) as experiment material for the hybridisation (controlled
breeding) proved to be good aid for his success, as it can be easily cross-pollinated.
(ii) Mendel selected true-breeding (pure) pea plants for his experiments.
(iii) He confined his study with two conditions of a single character at a time. When behaviour of one
character was established than he took two characters together and so on. This simplified the
observation to be made.
(iv) Mendel also kept accurate records of several generations, so that he could trace the ancestry of a
plant back from the beginning of the studies.
(v) The application of statistical methods and use of law of probability for analysing the results of
experiments was another key of Mendel's success.
(vi) Mendel was fortunate enough that the characters which he chosen for the crossing experiments in
garden pea did not show incomplete dominance, linkage to the genes of other characters and genes
interaction.
15) Write in a few lines about Watson and Crick Model of DNA molecule. Give its potential also.
Answer:
The DNA molecule has the form of a twisted ladder (figure). The vertical bars of the ladder are formed by alternating deoxyribose
sugar and phosphate components, while horizontal rings of the ladder are attached to the deoxyribose sugar components of the
vertical bars which are composed ofpurines and pyrimidines linked up through hydrogen bonds. 
16) How do industrial melanism confirms the natural selection theory of Darwinism?
Answer:
The replacement of white coloured moth by dark coloured melanic species due to industrial smoke is called industrial melanism.
It is a very nice example of natural selection in which a normal trait is changed in response to a changing environment to produce
better adapted individuals. This is because during industrialisation, the tree trunks covered by white lichens became dark due to
air pollution (dust and soot particles). Due to this, white-winged moths could be easily eaten by the predators as they failed in
camouflaging-(hide or disguise the pesence of a person, animal or object by means of camouflage).
17) How are biofertilizers different from fertilizers such as NPK that we buy in the market? Justify the role of Rhizobium as a
biofertilizer.
Answer:
NPK fertilizers are chemical fertilizers which are composed ofnitrogen(N), phosphorus(P) and potassium(K). Excessive use of
these chemical fertilizers causes deterioration of soil by destroying natural bacterial population and increased salt content of the
soil. While biofertilizers are organisms that enrich the quality of soil by natural process and do not harm the soil. The bacterium
Rhizobium present in the root nodules of leguminous plants fix atmospheric nitrogen thereby increasing the fertility of soil. Thus,
Rhizobium is a natural biofertilizer.   
18) What is meant by germplasm collection? What are its benefits?
Answer:
The collection of all the diverse alleles of all the genes of a crop plant is called germplasm collection.  It is of great benefits in
plant breeding programmes as it offers, to the breeders, the entire of genes and alleles and the characteristics which they
express. The breeder selects the most favourable characters of a particular gene and manipulates its transfer to a desirable
parent.
19) How the role of plant breeding is useful in food production?
Answer:
The main purpose of plant breeding is the genetic improvement of the crop in order to create desired plant type which are better
for cultivation and to give better yields. Most of the crops are originated from domesticated varieties, but now-a-days plant
breeding is carried out by using modern techniques or molecular genetic tools. By using this technology, we can improve the
quantity and quality of food production by keeping the following steps:
(a) Collection of variability.
(b) Evaluation and selection of parents.
(c) Cross hybridisation within the selected plants. 
The role of plant breeding has played an important role in food production:
(a) Lysine-rich maize kinds like Shakti, Rattan, Protina and others have been produced.
(b) By mutation breeding more than 200 kinds of crop have been produced.
(c) The quality of disease resistance in plants has been introduced by way of plant breeding.
(d) All sugarcane kinds are interspecific hybrids.
(e) The plant breeding has given the improved kinds of crops like Taichungnative-1 of rice and Sonora-
64 of wheat.
20) Explain gel electrophoresis. What are the steps involved in gel electrophoresis?
Answer:
Gel electrophoresis is a process for separating molecules by forcing them to migrate through a gel under
the influence of an electric field.
The steps involved in gel electrophoresis are -
(a) A gel of agarose or polyacrylamide is prepared (of specific porosity).
(b) DNA fragments of different lengths are allowed to move on gel in an electric field where DNA
fragments separate on the basis of size.
(c) It is 2-D technique to separate DNA fragments of a digest by endonuclease.
(d) DNA moves in buffer solution according to their molecular weight and size.
21)
Write short notes on
(i) Vector
(ii) Gene gun
(iii) rDNA technology.
Answer:
(i)  Vectors that help in gene cloning, e.g., plasmid, bacteriophage. They should have selectable marker
for identification of transformed cells.
(ii) Gene gun is a device for injecting cells with genetic information, originally designed for plant
transformation. The actual name of gene gun is the biolistic particle delivery system and this technique is
often simply referred to as biolistic.
(iii) Recombinant DNA (rDNA) technology hybridize genes of two different organisms to achieve desired
genotype and phenotype.
22)
(i) How is the greenhouse effect produced?
(ii) Explain the major harm caused by greenhouse gases.
Answer:
(i)  The glasswalls, high  content and high water vapour content inside the greenhouse let the
short-wave solar radiation enter but impede the exit of long-wave radiation emitted by the earth's
surface. This makes the greenhouse air warmer than outside air.
(ii) Greenhouse gases are mainly responsible for the enhanced greenhouse effect and global warming.
CFCs particularly are responsible for depletion of ozone layer and formation of ozone hole.
Page 5


d o n e Biology - Sample Paper-4
1) What is the function of fertilization?
Answer:
Fertilization is brought to transmission of genes from both parents to offspring. 
2) What are antigens?
Answer:
Any substance which, when introduced into the body, stimulates the production of antibody, is called antigen.   
3) What are bioreactors?
Answer:
Bioreactors are large vessels (having a volume of 100 to 1000l) in which raw materials are biologically, converted into specific
product by microbes, plant and animal cells or their enzymes.
4) Write the methods to introduce foreign DNA into host cell other than commonly used methods.
Answer:
Microinjection, direct DNA injection and gene gun.                                           
5) What do you mean by global warming?
Answer:
Global warming refers to the increase in the average temperature of the earth. It is caused by the enhanced greenhouse effect
due to the presence of greenhouse gases in higher concentration.  
6) Differentiate between binary fission and budding.
Answer:
Binary fission occurs in unicellular organisms like Amoeba and Paramecium, in which organism divides by cell division to give
two similar and equal organisms. While in budding the organism produces a small outgrowth or bud that grows in size and on
separation from parent forms new individual, e.g.. Hydra and Yeast.      
7)
(i) What is the significance of mutation?
(ii) Certain mutations are called silent mutation. How?
OR
What are linked genes? How can a pair of linked genes be identified?
Answer:
(i)  The sudden appearance or variations are called mutations. They lead to the new phenotypes. Though
mutations are random and occur at very slow rates, they are sufficient to create considerable genetic
variations for speciation to occur.
(ii) Silent mutation are those which:
(i) Occur at 3rd base position of codon.
(ii) Do not alter expression of the genes.                                  
OR
The genes present in the same chromosome and staying together during inheritance through generations
without any change are called linked genes. While unlinked genes are found on different
chromosomes.      
A pair of linked genes can be easily known from dihybrid cross experiments. The two linked genes do not
show independent assortment. They give dihybrid ratio of 3 : 1 instead of 9 : 3 : 3 : 1 and a test-cross ratio
1 : 1 instead of dihybrid test ratio 1:1:1:1.         
  
8) What is genetic difference in between Klinefelter's Syndrome and Turner's Syndrome?
Answer:
Klinefelter's Syndrome is genetic disorder cause due to the presence of an additional copy of X-chromosome resulting into a
karyotype of 47 (44A + XXY) chromosomes. While Turner's Syndrome is caused due to absent of one of the X-chromosome i.e.,
a karyotype of 45 (44A + XO). They are females whereas Klinefelter's are mostly males.
9) What is recombinant DNA technology? List the key tools used in recombinant DNA technology.
Answer:
Recombinant DNA technology, popularly called as genetic engineering, is a stream of biotechnology which deals with the
manipulation of genetic material by man in vitro. The key tools include restriction enzymes, polymerases, ligases, cloning vectors
& competent host organism.  
10) What is meant by ozone shield? How do CFC and ozone deplete substances affect ozone shield?
Answer:
In the stratosphere between 20-26 kms above sea level, there exist an ozone layer, averaging 0.29 cm above equator and exceed
40 cm above poles at end of winter season. This layer protects earth Biota from harmful effect of strong UV radiation and is
called ozone shield.               escape units stratosphere cause and destruction of  layer,
CFC, which produces 'active chlorine' in presence of UV radiation has most damaging effect. These radicals catalytically destroy
ozone of oxygen.  
11) Is it essential to provide sex education to adolescents? Comment.
Answer:
Sex education is essential to adolescents as it will provide right information to the young minds. It will discourage children from
believing in myths and having misconceptions about sex-related aspects. Proper information about reproductive organs, safe
and hygienic sexual practices, sexually transmitted diseases, AIDS, etc., would help those in adolescent age group to lead a
reproductively healthy life. 
12) What is multiple allelism? Explain.
Answer:
More than two alternate forms of gene present on the same locus called multiple alleles. There is absence of crossing over in
multiple alleles and the mode of inheritance in case of multiple alleles is called multiple allelism. The wellknown example of
multiple allele in human is blood group which also shows condominance. Landsteiner discovered the three blood groups in man
(A, B and 0). Multiple alleles express different alternatives of the same characters. 
13) Explain the permanent methods of birth control.
Answer:
Sterilisation provides a permanent birth control. It is called vasectomy in men and tubectomy in women. In vasectomy, a small
part of the vas deferens is removed or tied up through a small incision on the scrotum, whereas in tubectomy, a small part of the
fallopian tube is removed or tied up through a small incision in the abdomen, or through vagina. These techniques are highly
effective but their reversibility is very poor. 
14) Give the reasons for Mendel's success.
Answer:
Mendel succeeded in formulating the principles of heredity due to following reasons:
(i) The choice of garden pea (Pisum sativum) as experiment material for the hybridisation (controlled
breeding) proved to be good aid for his success, as it can be easily cross-pollinated.
(ii) Mendel selected true-breeding (pure) pea plants for his experiments.
(iii) He confined his study with two conditions of a single character at a time. When behaviour of one
character was established than he took two characters together and so on. This simplified the
observation to be made.
(iv) Mendel also kept accurate records of several generations, so that he could trace the ancestry of a
plant back from the beginning of the studies.
(v) The application of statistical methods and use of law of probability for analysing the results of
experiments was another key of Mendel's success.
(vi) Mendel was fortunate enough that the characters which he chosen for the crossing experiments in
garden pea did not show incomplete dominance, linkage to the genes of other characters and genes
interaction.
15) Write in a few lines about Watson and Crick Model of DNA molecule. Give its potential also.
Answer:
The DNA molecule has the form of a twisted ladder (figure). The vertical bars of the ladder are formed by alternating deoxyribose
sugar and phosphate components, while horizontal rings of the ladder are attached to the deoxyribose sugar components of the
vertical bars which are composed ofpurines and pyrimidines linked up through hydrogen bonds. 
16) How do industrial melanism confirms the natural selection theory of Darwinism?
Answer:
The replacement of white coloured moth by dark coloured melanic species due to industrial smoke is called industrial melanism.
It is a very nice example of natural selection in which a normal trait is changed in response to a changing environment to produce
better adapted individuals. This is because during industrialisation, the tree trunks covered by white lichens became dark due to
air pollution (dust and soot particles). Due to this, white-winged moths could be easily eaten by the predators as they failed in
camouflaging-(hide or disguise the pesence of a person, animal or object by means of camouflage).
17) How are biofertilizers different from fertilizers such as NPK that we buy in the market? Justify the role of Rhizobium as a
biofertilizer.
Answer:
NPK fertilizers are chemical fertilizers which are composed ofnitrogen(N), phosphorus(P) and potassium(K). Excessive use of
these chemical fertilizers causes deterioration of soil by destroying natural bacterial population and increased salt content of the
soil. While biofertilizers are organisms that enrich the quality of soil by natural process and do not harm the soil. The bacterium
Rhizobium present in the root nodules of leguminous plants fix atmospheric nitrogen thereby increasing the fertility of soil. Thus,
Rhizobium is a natural biofertilizer.   
18) What is meant by germplasm collection? What are its benefits?
Answer:
The collection of all the diverse alleles of all the genes of a crop plant is called germplasm collection.  It is of great benefits in
plant breeding programmes as it offers, to the breeders, the entire of genes and alleles and the characteristics which they
express. The breeder selects the most favourable characters of a particular gene and manipulates its transfer to a desirable
parent.
19) How the role of plant breeding is useful in food production?
Answer:
The main purpose of plant breeding is the genetic improvement of the crop in order to create desired plant type which are better
for cultivation and to give better yields. Most of the crops are originated from domesticated varieties, but now-a-days plant
breeding is carried out by using modern techniques or molecular genetic tools. By using this technology, we can improve the
quantity and quality of food production by keeping the following steps:
(a) Collection of variability.
(b) Evaluation and selection of parents.
(c) Cross hybridisation within the selected plants. 
The role of plant breeding has played an important role in food production:
(a) Lysine-rich maize kinds like Shakti, Rattan, Protina and others have been produced.
(b) By mutation breeding more than 200 kinds of crop have been produced.
(c) The quality of disease resistance in plants has been introduced by way of plant breeding.
(d) All sugarcane kinds are interspecific hybrids.
(e) The plant breeding has given the improved kinds of crops like Taichungnative-1 of rice and Sonora-
64 of wheat.
20) Explain gel electrophoresis. What are the steps involved in gel electrophoresis?
Answer:
Gel electrophoresis is a process for separating molecules by forcing them to migrate through a gel under
the influence of an electric field.
The steps involved in gel electrophoresis are -
(a) A gel of agarose or polyacrylamide is prepared (of specific porosity).
(b) DNA fragments of different lengths are allowed to move on gel in an electric field where DNA
fragments separate on the basis of size.
(c) It is 2-D technique to separate DNA fragments of a digest by endonuclease.
(d) DNA moves in buffer solution according to their molecular weight and size.
21)
Write short notes on
(i) Vector
(ii) Gene gun
(iii) rDNA technology.
Answer:
(i)  Vectors that help in gene cloning, e.g., plasmid, bacteriophage. They should have selectable marker
for identification of transformed cells.
(ii) Gene gun is a device for injecting cells with genetic information, originally designed for plant
transformation. The actual name of gene gun is the biolistic particle delivery system and this technique is
often simply referred to as biolistic.
(iii) Recombinant DNA (rDNA) technology hybridize genes of two different organisms to achieve desired
genotype and phenotype.
22)
(i) How is the greenhouse effect produced?
(ii) Explain the major harm caused by greenhouse gases.
Answer:
(i)  The glasswalls, high  content and high water vapour content inside the greenhouse let the
short-wave solar radiation enter but impede the exit of long-wave radiation emitted by the earth's
surface. This makes the greenhouse air warmer than outside air.
(ii) Greenhouse gases are mainly responsible for the enhanced greenhouse effect and global warming.
CFCs particularly are responsible for depletion of ozone layer and formation of ozone hole.
23)
Explain the cause of algal bloom in a water body. How does it affect an ecosystem?
OR
Define the terms.
(i) Adaptation
(ii) Alien's rule.
(iii) Commensalism
Answer:
Increased concentrations of phosphates and nitrates from industries, residential wastes as well as from agricultural runoff water
into the water bodies result in excessive growth of algae which form a mat on the surface of water. This phenomenon is called
algal bloom or eutrophication. It affects the ecosystem in following ways:
(a) It decreases light penetration thus affecting photosynthesis.
(b) It results in depletion of dissolved oxygen resulting in death of aquatic life.
(c) Nitrates contaminate drinking water leading to decrease in oxygen carrying capacity of haemoglobin
in human beings.
OR
(i)  Adaptations are the morphological, physiological or behavioural attributes that enable the organisms
to survive and reproduce in their habitat.
(ii) According to Alien's rule, "mammals from colder climatic region generally have shorter ears and limbs
to minimise heat loss".
(iii) Commensalism is the relationship which is beneficial for only one species and the other is neither
benefitted nor harmed.
24)
A biology teacher explain about the single cell protein (SCP) to his students. After completing his lecture
Kiran asked some question about SCP?
(i) What is SCP?
(ii) How it is important, nutritionally?
(iii) What are the component organisms in SCP?
(iv) What values are shown by Kiran as scientist?
Answer:
(i)  It refers to the source of mixed proteins extracted from pure or mixed culture of organism or cells. It
acts as a supplement protein with conventional food.
(ii) SCP is important for nutritional purpose as it contain about 60% digestable proteins.
(iii) The common microbes present in SCP are as follows.
Yeast, filamentous fungi, bacteria, cyanobacteria, algae, etc.  
(iv) Kiran has the attitude towards discovering new methods and inclined towards applied use of biology.
25)
We see advertisements like 'Saheli' as a method of family planning.
(i) What is 'Saheli'?
(ii) What is the principle behind using it as a method to control population growth?
(iii) How will you convenience people who say it is religiously wrong to use them to avoid pregnancy?
(iv) Mention the advantages of it.
OR
(i) Give the name of the structures, parts A and B shown in the diagram below develop into.