Biology: CBSE Sample Question Paper- 4 | Sample Papers for Class 12 Medical and Non-Medical PDF Download

 Page 1


d o n e Biology - Sample Paper-4
1) Name the hormones which stimulate the secretion of ovarian hormones.
Answer:
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) of anterior pituitary stimulate secretion of ovarian hormones.
2) Which disorder is caused in human by the presence of an extra 21 autosome?
Answer:
Down's syndrome.
3) Why are industrial effluent more difficult to manage than municipal sewage?
Answer:
Industrial effluents are more difficult to manage because it contains various types of non-biodegradable pollutants such as
heavy metal and acids.
4) Name a 'natural genetic engineer' of plants.
Answer:
Agrobacterium tumefactions, a crown gall bacterium, is called natural genetic engineer of plants.
5) Mention the uses of IUCN Red List.
Answer:
IUCN red list helps in (a) identification and documentation of endangered species. (b) developing awareness about the
importance of threatened species.
6)
Name any two plants which flower only once in their life time after passing through a very long vegetative
phase.
OR
How incompatibility acts as a natural barrier in the fusion of gametes?
Answer:
(a) Bamboo species flower only once in their life time, generally after 50-100 years and produce large
number of fruits and ultimately die.
(b) Strobilanthus Kunthiana (neelakuranji) flowers once in 12 years. Recently, this plant flowered during
September-October 2006.
OR
Incompatibility is the inability of gametes to fuse in genetically similar plants. It is controlled by genes
with multiple alleles called S-allele. This phenomenon is also called intraspecific incompatibility. It
involves many intricate mechanisms associated with stigmatic tissues and pollen grain.
7) What acts as an inducer in lac operon? How does it switch on the operon?
Answer:
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon. Hence is termed
as inducer. The lactose inactivates the represser by interaction with it, hence represser does not block the operator region. This
allow RNA polymerase access to the promoter and transcription of lac mRNA.
8) Mention two applications of tissue culture. Explain any one.
Answer:
  
Page 2


d o n e Biology - Sample Paper-4
1) Name the hormones which stimulate the secretion of ovarian hormones.
Answer:
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) of anterior pituitary stimulate secretion of ovarian hormones.
2) Which disorder is caused in human by the presence of an extra 21 autosome?
Answer:
Down's syndrome.
3) Why are industrial effluent more difficult to manage than municipal sewage?
Answer:
Industrial effluents are more difficult to manage because it contains various types of non-biodegradable pollutants such as
heavy metal and acids.
4) Name a 'natural genetic engineer' of plants.
Answer:
Agrobacterium tumefactions, a crown gall bacterium, is called natural genetic engineer of plants.
5) Mention the uses of IUCN Red List.
Answer:
IUCN red list helps in (a) identification and documentation of endangered species. (b) developing awareness about the
importance of threatened species.
6)
Name any two plants which flower only once in their life time after passing through a very long vegetative
phase.
OR
How incompatibility acts as a natural barrier in the fusion of gametes?
Answer:
(a) Bamboo species flower only once in their life time, generally after 50-100 years and produce large
number of fruits and ultimately die.
(b) Strobilanthus Kunthiana (neelakuranji) flowers once in 12 years. Recently, this plant flowered during
September-October 2006.
OR
Incompatibility is the inability of gametes to fuse in genetically similar plants. It is controlled by genes
with multiple alleles called S-allele. This phenomenon is also called intraspecific incompatibility. It
involves many intricate mechanisms associated with stigmatic tissues and pollen grain.
7) What acts as an inducer in lac operon? How does it switch on the operon?
Answer:
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon. Hence is termed
as inducer. The lactose inactivates the represser by interaction with it, hence represser does not block the operator region. This
allow RNA polymerase access to the promoter and transcription of lac mRNA.
8) Mention two applications of tissue culture. Explain any one.
Answer:
  
Micro-propagation and development oftransgenic plants are done by the technique of tissue culture are done by the technique of
tissue culture. Micropropagation is the practice of rapidly multiplying stock plant material to produce a large number of progeny
plants, using modern plant tissue culture methods.
9)
(i) Define brood parasitism in relation to birds.
(ii) State Cause's "competitive exclusion principle".
Answer:
(i)  Brood parasitism is a type of parasitism in which the parasitic bird lays its eggs in the nest of its host
and let the host bird to incubate them.
(ii) According to Cause's "competitive exclusion principle", "the two closely related species competing for
the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated
eventually."
10) Give advantages of CNG over petrol or diesel.
Answer:
(a) CNG is better than petrol or diesel because it bums most efficiently and very little of it is left
unbumt.
(b) It is cheaper than petrol or diesel.
(c) It cannot be siphoned off by thieves.
(d) It cannot be adulterated like petrol or diesel.     
11) Why is the fertilisation in case of angiosperms referred to as double fertilisation? Give the significance of double
fertilisation."
Answer:
Fertilisation in angiospermic flowering plants is known as double fertilisation because both the male gametes of a male
gametophyte take parts in sexual fusion. One fuses with egg to give rise a diploid zygote while the other male gamete fuses with
two polar nuclei (secondary diploid nucleus) to form the triploid primary endosperm nucleus (PEN). Thus, double fusion occurs in
an embryo sac during fertilisation. Double fertilisation results the formation of triploid endosperm which provide sufficient
nutritional food to the developing embryo and seed. Endosperm helps in the production of healthy seeds. Thus, triploid
endosperm compensates for the extreme reduced female gametophyte of angiosperms.
12) Differentiate between test cross and backcrosa"
Answer:
Test cross : Cross between  and recessive parent/to determine genotype of  Back cross: Cross between
 and any of dominant phenotype parent/need not be a test cross/ to establish. It is used in crop/homozygosity
improvement.
13) Write a note on barrier methods of contraception
Answer:
In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers. (a) Condoms are barriers
made of thin rubber/latex sheath that are used to cover penis in the male or vagina and cervix in the female, just before coitus.
Nirodh is a popular brand of condom for the male. (b) Diaphragms, cervical caps and vaults are also barriers made of rubber that
are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of
sperms through the cervix.
14)
(i) In monohybrid cross of red and white flower, Mendel got only red flower. On setting the plants
having red flower he got both plants with red and white flower. Explain the basis of using RR and rr
symbols to represent the genotype of plants of parental generation
Page 3


d o n e Biology - Sample Paper-4
1) Name the hormones which stimulate the secretion of ovarian hormones.
Answer:
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) of anterior pituitary stimulate secretion of ovarian hormones.
2) Which disorder is caused in human by the presence of an extra 21 autosome?
Answer:
Down's syndrome.
3) Why are industrial effluent more difficult to manage than municipal sewage?
Answer:
Industrial effluents are more difficult to manage because it contains various types of non-biodegradable pollutants such as
heavy metal and acids.
4) Name a 'natural genetic engineer' of plants.
Answer:
Agrobacterium tumefactions, a crown gall bacterium, is called natural genetic engineer of plants.
5) Mention the uses of IUCN Red List.
Answer:
IUCN red list helps in (a) identification and documentation of endangered species. (b) developing awareness about the
importance of threatened species.
6)
Name any two plants which flower only once in their life time after passing through a very long vegetative
phase.
OR
How incompatibility acts as a natural barrier in the fusion of gametes?
Answer:
(a) Bamboo species flower only once in their life time, generally after 50-100 years and produce large
number of fruits and ultimately die.
(b) Strobilanthus Kunthiana (neelakuranji) flowers once in 12 years. Recently, this plant flowered during
September-October 2006.
OR
Incompatibility is the inability of gametes to fuse in genetically similar plants. It is controlled by genes
with multiple alleles called S-allele. This phenomenon is also called intraspecific incompatibility. It
involves many intricate mechanisms associated with stigmatic tissues and pollen grain.
7) What acts as an inducer in lac operon? How does it switch on the operon?
Answer:
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon. Hence is termed
as inducer. The lactose inactivates the represser by interaction with it, hence represser does not block the operator region. This
allow RNA polymerase access to the promoter and transcription of lac mRNA.
8) Mention two applications of tissue culture. Explain any one.
Answer:
  
Micro-propagation and development oftransgenic plants are done by the technique of tissue culture are done by the technique of
tissue culture. Micropropagation is the practice of rapidly multiplying stock plant material to produce a large number of progeny
plants, using modern plant tissue culture methods.
9)
(i) Define brood parasitism in relation to birds.
(ii) State Cause's "competitive exclusion principle".
Answer:
(i)  Brood parasitism is a type of parasitism in which the parasitic bird lays its eggs in the nest of its host
and let the host bird to incubate them.
(ii) According to Cause's "competitive exclusion principle", "the two closely related species competing for
the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated
eventually."
10) Give advantages of CNG over petrol or diesel.
Answer:
(a) CNG is better than petrol or diesel because it bums most efficiently and very little of it is left
unbumt.
(b) It is cheaper than petrol or diesel.
(c) It cannot be siphoned off by thieves.
(d) It cannot be adulterated like petrol or diesel.     
11) Why is the fertilisation in case of angiosperms referred to as double fertilisation? Give the significance of double
fertilisation."
Answer:
Fertilisation in angiospermic flowering plants is known as double fertilisation because both the male gametes of a male
gametophyte take parts in sexual fusion. One fuses with egg to give rise a diploid zygote while the other male gamete fuses with
two polar nuclei (secondary diploid nucleus) to form the triploid primary endosperm nucleus (PEN). Thus, double fusion occurs in
an embryo sac during fertilisation. Double fertilisation results the formation of triploid endosperm which provide sufficient
nutritional food to the developing embryo and seed. Endosperm helps in the production of healthy seeds. Thus, triploid
endosperm compensates for the extreme reduced female gametophyte of angiosperms.
12) Differentiate between test cross and backcrosa"
Answer:
Test cross : Cross between  and recessive parent/to determine genotype of  Back cross: Cross between
 and any of dominant phenotype parent/need not be a test cross/ to establish. It is used in crop/homozygosity
improvement.
13) Write a note on barrier methods of contraception
Answer:
In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers. (a) Condoms are barriers
made of thin rubber/latex sheath that are used to cover penis in the male or vagina and cervix in the female, just before coitus.
Nirodh is a popular brand of condom for the male. (b) Diaphragms, cervical caps and vaults are also barriers made of rubber that
are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of
sperms through the cervix.
14)
(i) In monohybrid cross of red and white flower, Mendel got only red flower. On setting the plants
having red flower he got both plants with red and white flower. Explain the basis of using RR and rr
symbols to represent the genotype of plants of parental generation
(ii) A, B, D are three independently assorting genes with their recessive alleles a, b, d, respectively. A
cross was made between individuals of AabbDD genotype with aabbdd. Explain the type of genotypes of
the offspring produced
(iii) A progeny of  is crossed with the homozygous recessive parent. What is this cross called?
Work out how is it useful?
Answer:
(i)  On crossing red and white flower only red colour flower appeared in the F, generation. But the white
colour flower again appear in the  generation which is raised out of the individuals only.
Mendel found that there is factor of each and every character. Accordingly, there has to be one factor (R)
for red flower and other one factor (r) for white flower. In case, an organism possess only one copy of the
gene then the possibility of reappearance of white flower in the K generation of the given cross is not there.
Also the ratio (3:1 or red and white) indicates that each organism must possess two copies of a particular
gene.
(ii) The given cross is Aa bb DDX aa bb dd
Accordingly the type of offspring produced would be
(iii) When a progeny of  is crossed with the homozygous recessive parent, it is called test cross.
Such a cross is useful to determine the genotype of an unknown i.e. whether it is heterozygous, or
homozygous dominant for the trait.
15)
(i) What are the characteristic feautures of a true-breeding line?
(ii) In peas, tallness is dominant over dwarfhess, and red colour of flowers is dominant over the white
colour. When a tall plant bearing red flowers was pollinated by a dwarf plant bearing white flowers, the
different phenotypic groups were obtained in the progeny in numbers mentioned against them.
Tall, Red =138
Tall, White =132
Dwarf, Red =136
Dwarf, White =128
Mention the genotypes of the two parents and of the types of four off springs.
Answer:
(i)  A true-breeding line for a trait is one that, has undergone continuous self-pollination or brother-sister mating, showing a
stability in the inheritance of the trait for several generations.  (ii) The result shows that the four types of offspring are in a ratio of
1 : 1: 1: 1. Such a result is observed in a test-cross progeny of adihybridcross. The cross can be represented as: Tall & Red 
Dwarf & White (Tt Rr)                           (ttrr) TR Tr                           tr            
tr
TR TrRr Tall Red
Tr Ttee Tall White
tR TtRr Dwarf Red
tr ttrr Dwarf white
16) Write a note on single cell protein.
Answer:
The protein deficiency is a large and alarming-problem as the maximum human population is suffering from malnutrition and this
problem can be solved by obtaining the protein and vitamin by moulds (mushrooms, yeasts etc.) with the help of
microorganisms. The edible proteins can be produced on a large scale by means of microorganisms for the use of animal and
human nutrition is called single cell protein.    The common microorganisms, which are used in production of single cell protein,
are (i) yeast (ii) algae, (iii) moulds (Aspergillus, Penicillium, etc). The production of protein by those microorganisms is very high
and most satisfactory as the microorganisms grow very fast and synthesise proteins.
17) What is apiculture? How it is important?
Page 4


d o n e Biology - Sample Paper-4
1) Name the hormones which stimulate the secretion of ovarian hormones.
Answer:
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) of anterior pituitary stimulate secretion of ovarian hormones.
2) Which disorder is caused in human by the presence of an extra 21 autosome?
Answer:
Down's syndrome.
3) Why are industrial effluent more difficult to manage than municipal sewage?
Answer:
Industrial effluents are more difficult to manage because it contains various types of non-biodegradable pollutants such as
heavy metal and acids.
4) Name a 'natural genetic engineer' of plants.
Answer:
Agrobacterium tumefactions, a crown gall bacterium, is called natural genetic engineer of plants.
5) Mention the uses of IUCN Red List.
Answer:
IUCN red list helps in (a) identification and documentation of endangered species. (b) developing awareness about the
importance of threatened species.
6)
Name any two plants which flower only once in their life time after passing through a very long vegetative
phase.
OR
How incompatibility acts as a natural barrier in the fusion of gametes?
Answer:
(a) Bamboo species flower only once in their life time, generally after 50-100 years and produce large
number of fruits and ultimately die.
(b) Strobilanthus Kunthiana (neelakuranji) flowers once in 12 years. Recently, this plant flowered during
September-October 2006.
OR
Incompatibility is the inability of gametes to fuse in genetically similar plants. It is controlled by genes
with multiple alleles called S-allele. This phenomenon is also called intraspecific incompatibility. It
involves many intricate mechanisms associated with stigmatic tissues and pollen grain.
7) What acts as an inducer in lac operon? How does it switch on the operon?
Answer:
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon. Hence is termed
as inducer. The lactose inactivates the represser by interaction with it, hence represser does not block the operator region. This
allow RNA polymerase access to the promoter and transcription of lac mRNA.
8) Mention two applications of tissue culture. Explain any one.
Answer:
  
Micro-propagation and development oftransgenic plants are done by the technique of tissue culture are done by the technique of
tissue culture. Micropropagation is the practice of rapidly multiplying stock plant material to produce a large number of progeny
plants, using modern plant tissue culture methods.
9)
(i) Define brood parasitism in relation to birds.
(ii) State Cause's "competitive exclusion principle".
Answer:
(i)  Brood parasitism is a type of parasitism in which the parasitic bird lays its eggs in the nest of its host
and let the host bird to incubate them.
(ii) According to Cause's "competitive exclusion principle", "the two closely related species competing for
the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated
eventually."
10) Give advantages of CNG over petrol or diesel.
Answer:
(a) CNG is better than petrol or diesel because it bums most efficiently and very little of it is left
unbumt.
(b) It is cheaper than petrol or diesel.
(c) It cannot be siphoned off by thieves.
(d) It cannot be adulterated like petrol or diesel.     
11) Why is the fertilisation in case of angiosperms referred to as double fertilisation? Give the significance of double
fertilisation."
Answer:
Fertilisation in angiospermic flowering plants is known as double fertilisation because both the male gametes of a male
gametophyte take parts in sexual fusion. One fuses with egg to give rise a diploid zygote while the other male gamete fuses with
two polar nuclei (secondary diploid nucleus) to form the triploid primary endosperm nucleus (PEN). Thus, double fusion occurs in
an embryo sac during fertilisation. Double fertilisation results the formation of triploid endosperm which provide sufficient
nutritional food to the developing embryo and seed. Endosperm helps in the production of healthy seeds. Thus, triploid
endosperm compensates for the extreme reduced female gametophyte of angiosperms.
12) Differentiate between test cross and backcrosa"
Answer:
Test cross : Cross between  and recessive parent/to determine genotype of  Back cross: Cross between
 and any of dominant phenotype parent/need not be a test cross/ to establish. It is used in crop/homozygosity
improvement.
13) Write a note on barrier methods of contraception
Answer:
In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers. (a) Condoms are barriers
made of thin rubber/latex sheath that are used to cover penis in the male or vagina and cervix in the female, just before coitus.
Nirodh is a popular brand of condom for the male. (b) Diaphragms, cervical caps and vaults are also barriers made of rubber that
are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of
sperms through the cervix.
14)
(i) In monohybrid cross of red and white flower, Mendel got only red flower. On setting the plants
having red flower he got both plants with red and white flower. Explain the basis of using RR and rr
symbols to represent the genotype of plants of parental generation
(ii) A, B, D are three independently assorting genes with their recessive alleles a, b, d, respectively. A
cross was made between individuals of AabbDD genotype with aabbdd. Explain the type of genotypes of
the offspring produced
(iii) A progeny of  is crossed with the homozygous recessive parent. What is this cross called?
Work out how is it useful?
Answer:
(i)  On crossing red and white flower only red colour flower appeared in the F, generation. But the white
colour flower again appear in the  generation which is raised out of the individuals only.
Mendel found that there is factor of each and every character. Accordingly, there has to be one factor (R)
for red flower and other one factor (r) for white flower. In case, an organism possess only one copy of the
gene then the possibility of reappearance of white flower in the K generation of the given cross is not there.
Also the ratio (3:1 or red and white) indicates that each organism must possess two copies of a particular
gene.
(ii) The given cross is Aa bb DDX aa bb dd
Accordingly the type of offspring produced would be
(iii) When a progeny of  is crossed with the homozygous recessive parent, it is called test cross.
Such a cross is useful to determine the genotype of an unknown i.e. whether it is heterozygous, or
homozygous dominant for the trait.
15)
(i) What are the characteristic feautures of a true-breeding line?
(ii) In peas, tallness is dominant over dwarfhess, and red colour of flowers is dominant over the white
colour. When a tall plant bearing red flowers was pollinated by a dwarf plant bearing white flowers, the
different phenotypic groups were obtained in the progeny in numbers mentioned against them.
Tall, Red =138
Tall, White =132
Dwarf, Red =136
Dwarf, White =128
Mention the genotypes of the two parents and of the types of four off springs.
Answer:
(i)  A true-breeding line for a trait is one that, has undergone continuous self-pollination or brother-sister mating, showing a
stability in the inheritance of the trait for several generations.  (ii) The result shows that the four types of offspring are in a ratio of
1 : 1: 1: 1. Such a result is observed in a test-cross progeny of adihybridcross. The cross can be represented as: Tall & Red 
Dwarf & White (Tt Rr)                           (ttrr) TR Tr                           tr            
tr
TR TrRr Tall Red
Tr Ttee Tall White
tR TtRr Dwarf Red
tr ttrr Dwarf white
16) Write a note on single cell protein.
Answer:
The protein deficiency is a large and alarming-problem as the maximum human population is suffering from malnutrition and this
problem can be solved by obtaining the protein and vitamin by moulds (mushrooms, yeasts etc.) with the help of
microorganisms. The edible proteins can be produced on a large scale by means of microorganisms for the use of animal and
human nutrition is called single cell protein.    The common microorganisms, which are used in production of single cell protein,
are (i) yeast (ii) algae, (iii) moulds (Aspergillus, Penicillium, etc). The production of protein by those microorganisms is very high
and most satisfactory as the microorganisms grow very fast and synthesise proteins.
17) What is apiculture? How it is important?
Answer:
Bee-keeping is also known as apiculture which is concerned with agriculture with the maintenance of hives of honeybees for the
commercial production of honey and wax. Honey is sweet and of high nutritive value and contains sugar, water, vitamins,
minerals, enzymes, amino acids. It has importance in pharmaceuticals and the treatment of various disorders related to
digestion, vomiting and liver ailments.
18)
(i) What is golden rice?
(ii) What is gene therapy? Can it be used for treatment of sickle -cell anaemia, haemophilia and
thalassemia?
Answer:
(i)  Golden rice is transgenic rice having gene for synthesis of vitamin A.                                     
(ii) Gene therapy is alteration of specific genes to modify the patient's genotype for the treatment of
hereditary diseases like haemophilia and phenylketonuria. Yes, It can be used for treatment of sickle cell
anaemia, haemophilia and thalassemia by transplanting defective genes by correct ones.
19)
What is vector?
(ii) Name the two types of cloning vectors.
(iii) Which cloning vector was discovered first time?
Answer:
(i) Vector is DNA molecule that can carry a foreign DNA segment and replicates inside the host cell.
(ii) (a) Plasmid vectors and (b) Bacteriophage vectors.    
(iii) E. coli cloning vector  
20) How a transgenic plant got itself protected from nematode infestation?
Answer:
A transgenic plant protected from nematode infestation by using Agrobacterium as vectors. The nematode specific genes were
introduced into the host plant. The introduction of DNA was such that it produced both sense and antisense RNA in host cells.
These two RNA's being complementary to each other formed a double stranded RNA (dsRNA) that initiated RNA; and thus,
silenced the specific mRNA of the nematode. As a result, the parasite could not survive in a transgenic host expressing specific
interfering RNA. Thus, the transgenic plant got itself protected from the nematode parasite.  
21) Write an account of the various factors which affect the population density in the habitat.
Answer:
There are four factors which affect the population density in a habitat.
(a) Natality refers to the number of births during a given period in the population that are added to the
initial density.
(b) Mortality is the number of deaths in the population during a given period.     
(c) Immigration is the number of individuals of the same species that have come into the habitat from
elsewhere during the time period under consideration.
(d) Emigration is the number of individuals of the population who left the habitat and gone elsewhere
during the time period under consideration.        
22)
Expain the following.
(i) Phosphorus cycle
(ii) Pyramid of energy.
Answer:
Page 5


d o n e Biology - Sample Paper-4
1) Name the hormones which stimulate the secretion of ovarian hormones.
Answer:
Follicle stimulating hormone (FSH) and Luteinising hormone (LH) of anterior pituitary stimulate secretion of ovarian hormones.
2) Which disorder is caused in human by the presence of an extra 21 autosome?
Answer:
Down's syndrome.
3) Why are industrial effluent more difficult to manage than municipal sewage?
Answer:
Industrial effluents are more difficult to manage because it contains various types of non-biodegradable pollutants such as
heavy metal and acids.
4) Name a 'natural genetic engineer' of plants.
Answer:
Agrobacterium tumefactions, a crown gall bacterium, is called natural genetic engineer of plants.
5) Mention the uses of IUCN Red List.
Answer:
IUCN red list helps in (a) identification and documentation of endangered species. (b) developing awareness about the
importance of threatened species.
6)
Name any two plants which flower only once in their life time after passing through a very long vegetative
phase.
OR
How incompatibility acts as a natural barrier in the fusion of gametes?
Answer:
(a) Bamboo species flower only once in their life time, generally after 50-100 years and produce large
number of fruits and ultimately die.
(b) Strobilanthus Kunthiana (neelakuranji) flowers once in 12 years. Recently, this plant flowered during
September-October 2006.
OR
Incompatibility is the inability of gametes to fuse in genetically similar plants. It is controlled by genes
with multiple alleles called S-allele. This phenomenon is also called intraspecific incompatibility. It
involves many intricate mechanisms associated with stigmatic tissues and pollen grain.
7) What acts as an inducer in lac operon? How does it switch on the operon?
Answer:
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon. Hence is termed
as inducer. The lactose inactivates the represser by interaction with it, hence represser does not block the operator region. This
allow RNA polymerase access to the promoter and transcription of lac mRNA.
8) Mention two applications of tissue culture. Explain any one.
Answer:
  
Micro-propagation and development oftransgenic plants are done by the technique of tissue culture are done by the technique of
tissue culture. Micropropagation is the practice of rapidly multiplying stock plant material to produce a large number of progeny
plants, using modern plant tissue culture methods.
9)
(i) Define brood parasitism in relation to birds.
(ii) State Cause's "competitive exclusion principle".
Answer:
(i)  Brood parasitism is a type of parasitism in which the parasitic bird lays its eggs in the nest of its host
and let the host bird to incubate them.
(ii) According to Cause's "competitive exclusion principle", "the two closely related species competing for
the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated
eventually."
10) Give advantages of CNG over petrol or diesel.
Answer:
(a) CNG is better than petrol or diesel because it bums most efficiently and very little of it is left
unbumt.
(b) It is cheaper than petrol or diesel.
(c) It cannot be siphoned off by thieves.
(d) It cannot be adulterated like petrol or diesel.     
11) Why is the fertilisation in case of angiosperms referred to as double fertilisation? Give the significance of double
fertilisation."
Answer:
Fertilisation in angiospermic flowering plants is known as double fertilisation because both the male gametes of a male
gametophyte take parts in sexual fusion. One fuses with egg to give rise a diploid zygote while the other male gamete fuses with
two polar nuclei (secondary diploid nucleus) to form the triploid primary endosperm nucleus (PEN). Thus, double fusion occurs in
an embryo sac during fertilisation. Double fertilisation results the formation of triploid endosperm which provide sufficient
nutritional food to the developing embryo and seed. Endosperm helps in the production of healthy seeds. Thus, triploid
endosperm compensates for the extreme reduced female gametophyte of angiosperms.
12) Differentiate between test cross and backcrosa"
Answer:
Test cross : Cross between  and recessive parent/to determine genotype of  Back cross: Cross between
 and any of dominant phenotype parent/need not be a test cross/ to establish. It is used in crop/homozygosity
improvement.
13) Write a note on barrier methods of contraception
Answer:
In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers. (a) Condoms are barriers
made of thin rubber/latex sheath that are used to cover penis in the male or vagina and cervix in the female, just before coitus.
Nirodh is a popular brand of condom for the male. (b) Diaphragms, cervical caps and vaults are also barriers made of rubber that
are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of
sperms through the cervix.
14)
(i) In monohybrid cross of red and white flower, Mendel got only red flower. On setting the plants
having red flower he got both plants with red and white flower. Explain the basis of using RR and rr
symbols to represent the genotype of plants of parental generation
(ii) A, B, D are three independently assorting genes with their recessive alleles a, b, d, respectively. A
cross was made between individuals of AabbDD genotype with aabbdd. Explain the type of genotypes of
the offspring produced
(iii) A progeny of  is crossed with the homozygous recessive parent. What is this cross called?
Work out how is it useful?
Answer:
(i)  On crossing red and white flower only red colour flower appeared in the F, generation. But the white
colour flower again appear in the  generation which is raised out of the individuals only.
Mendel found that there is factor of each and every character. Accordingly, there has to be one factor (R)
for red flower and other one factor (r) for white flower. In case, an organism possess only one copy of the
gene then the possibility of reappearance of white flower in the K generation of the given cross is not there.
Also the ratio (3:1 or red and white) indicates that each organism must possess two copies of a particular
gene.
(ii) The given cross is Aa bb DDX aa bb dd
Accordingly the type of offspring produced would be
(iii) When a progeny of  is crossed with the homozygous recessive parent, it is called test cross.
Such a cross is useful to determine the genotype of an unknown i.e. whether it is heterozygous, or
homozygous dominant for the trait.
15)
(i) What are the characteristic feautures of a true-breeding line?
(ii) In peas, tallness is dominant over dwarfhess, and red colour of flowers is dominant over the white
colour. When a tall plant bearing red flowers was pollinated by a dwarf plant bearing white flowers, the
different phenotypic groups were obtained in the progeny in numbers mentioned against them.
Tall, Red =138
Tall, White =132
Dwarf, Red =136
Dwarf, White =128
Mention the genotypes of the two parents and of the types of four off springs.
Answer:
(i)  A true-breeding line for a trait is one that, has undergone continuous self-pollination or brother-sister mating, showing a
stability in the inheritance of the trait for several generations.  (ii) The result shows that the four types of offspring are in a ratio of
1 : 1: 1: 1. Such a result is observed in a test-cross progeny of adihybridcross. The cross can be represented as: Tall & Red 
Dwarf & White (Tt Rr)                           (ttrr) TR Tr                           tr            
tr
TR TrRr Tall Red
Tr Ttee Tall White
tR TtRr Dwarf Red
tr ttrr Dwarf white
16) Write a note on single cell protein.
Answer:
The protein deficiency is a large and alarming-problem as the maximum human population is suffering from malnutrition and this
problem can be solved by obtaining the protein and vitamin by moulds (mushrooms, yeasts etc.) with the help of
microorganisms. The edible proteins can be produced on a large scale by means of microorganisms for the use of animal and
human nutrition is called single cell protein.    The common microorganisms, which are used in production of single cell protein,
are (i) yeast (ii) algae, (iii) moulds (Aspergillus, Penicillium, etc). The production of protein by those microorganisms is very high
and most satisfactory as the microorganisms grow very fast and synthesise proteins.
17) What is apiculture? How it is important?
Answer:
Bee-keeping is also known as apiculture which is concerned with agriculture with the maintenance of hives of honeybees for the
commercial production of honey and wax. Honey is sweet and of high nutritive value and contains sugar, water, vitamins,
minerals, enzymes, amino acids. It has importance in pharmaceuticals and the treatment of various disorders related to
digestion, vomiting and liver ailments.
18)
(i) What is golden rice?
(ii) What is gene therapy? Can it be used for treatment of sickle -cell anaemia, haemophilia and
thalassemia?
Answer:
(i)  Golden rice is transgenic rice having gene for synthesis of vitamin A.                                     
(ii) Gene therapy is alteration of specific genes to modify the patient's genotype for the treatment of
hereditary diseases like haemophilia and phenylketonuria. Yes, It can be used for treatment of sickle cell
anaemia, haemophilia and thalassemia by transplanting defective genes by correct ones.
19)
What is vector?
(ii) Name the two types of cloning vectors.
(iii) Which cloning vector was discovered first time?
Answer:
(i) Vector is DNA molecule that can carry a foreign DNA segment and replicates inside the host cell.
(ii) (a) Plasmid vectors and (b) Bacteriophage vectors.    
(iii) E. coli cloning vector  
20) How a transgenic plant got itself protected from nematode infestation?
Answer:
A transgenic plant protected from nematode infestation by using Agrobacterium as vectors. The nematode specific genes were
introduced into the host plant. The introduction of DNA was such that it produced both sense and antisense RNA in host cells.
These two RNA's being complementary to each other formed a double stranded RNA (dsRNA) that initiated RNA; and thus,
silenced the specific mRNA of the nematode. As a result, the parasite could not survive in a transgenic host expressing specific
interfering RNA. Thus, the transgenic plant got itself protected from the nematode parasite.  
21) Write an account of the various factors which affect the population density in the habitat.
Answer:
There are four factors which affect the population density in a habitat.
(a) Natality refers to the number of births during a given period in the population that are added to the
initial density.
(b) Mortality is the number of deaths in the population during a given period.     
(c) Immigration is the number of individuals of the same species that have come into the habitat from
elsewhere during the time period under consideration.
(d) Emigration is the number of individuals of the population who left the habitat and gone elsewhere
during the time period under consideration.        
22)
Expain the following.
(i) Phosphorus cycle
(ii) Pyramid of energy.
Answer:
(i)  Phosphorus cycle: Phosphorus has a sedimentary cycle. Phosphorus is deposited into the soil from the
phosphate rocks and occurs in the soil in the form of orthophosphates. Absorption of phosphate is
facilitated by mycorrhiza. Animals take this phosphorus by the way of food. Dead and worn out plant and
animal parts become decayed. They are acted upon by phosphatising bacteria to release phosphorus in
the soil.  
(ii) Pyramid of energy: It is graphic representation of amount of energy trapped per unit time and area in
different trophic levels of a food chain with producers forming the base and top carnivores the tip.
Maximum energy content is present in producers. They convert solar energy in chemical form and stored
inside organic matter manufactured by the producers.
Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular
trophic level to the next trophic level, some energy is always lost as heat at each step.               
23)
Discuss the following:
(i) Chipko Movement
(ii) Radioactive wastes.
Answer:
(i) Chipko movement: Chipko movement was an organised resistance to the destruction of forests. It
started in 1970s in Garhwal Himalayas and spread throughout India. The name of the movement comes
from the word "embrace", as the villagers hugged the trees, and prevented the contractors from falling
them. Mr. Sunderlal Bahuguna, a Gandhian activist and philosopher was the leader of Chipko Movement. 
(ii) Radioactive wastes: Radioactive wastes such as uranium, are used as fuel in the atomic power plants.
The accident leakage and disposal of radioactive wastes is the most serious problem. All safety measures
for this purpose should be strictly enforced. High-level radioactive wastes generate a lot of heat and thus
require cooling, as well as special protective shields during handling and transport.
24) Nisha was rushed to a nearby hospital after an severe accident, which caused much blood loss. Nisha had O negative blood
group and the hospital failed to supply O negative blood for transfusion. Ahmed, who was attending a patient heard about the
situation and agreed to donate blood as he had same blood group. Nisha's mother initially refused to take blood from Ahmed
due to religion issues but was later was convinced by her son's view.
(i) Why can't O positive blood be tranfused into Nisha's body?
(ii) What is the genetic basis of blood group inheritance?
(iii) Human blood grouping is an example of.
(iv) What values do you find in Nisha's brother and Ahmed?
Answer:
(i)   blood group contains antigen for Rh factor.  blood lacks the antigen so, if the two blood mix, it shall cause
clotting resulting in death of the patient. (ii) Human blood groups are A, B, AB, O. Four phenotypes are expressed by paired
combination of three alleles . and  are dominant alleles for blood group A and B respectively. O
blood group is due to lack of any dominant gene. Alleles  expresses both dominant traits and the blood group is
AB. 
Blood type (phenotype) Genotype Can Receive Blood from
A A or O
B B or O
AB A, B, AB, O
O O
(iii) Multiple alleles.       (iv) Nisha's brother shown understanding of science and Ahmed believes in helping a person in need without thinking about which
religion or caste he belongs to.   
25)
What develops into a microspore mother cell in a flower? Trace the development of this cell into a pollen
grain which is ready for germination.
OR
A woman has conceived and implantation has occurred within her uterus. Describe the sequence of
changes that would take place in her body up to parturition under the influence of various hormones.
Answer: