Biology: CBSE Sample Question Paper- 7 | Sample Papers for Class 12 Medical and Non-Medical PDF Download

 Page 1


d o n e Biology - Sample Paper-8
1) A haeomophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
Answer:
Father  (Haemophilia); Mother XX (Normal homozygous)  So, the probability to have
haemophilic daughter will be 0%.
2) Differentiate between DNA and DNase.
Answer:
DNA is the deoxyribonucleic acid found in nucleus of a cell, while DNase is the catalytic enzyme used to cleave phosphodiester
linkage in the DNA.
3) Give the name of the causative agent of amoebiasis and write its any two symptoms.
Answer:
Entamoeba histolytica is a protozoan parasite in the large intestine of human. Symptoms include abdominal pain and cramps,
stool with excess mucous and blood clots.
4) Would you choose an exonuclease for producing recombinant DNA molecule?
Answer:
No, because exonuclease removes nucleotides from the terminal end (either 5' or 3') of DNA in one strand.
5) While doing a PCR, denaturation step is missed. What will be its effect on the process?
Answer:
If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template. No extension
will take place, hence no amplification will occur.
6) Why is pedigree analysis done in humans? List two reasons why the Mendelian experiments cannot be carried out in human
beings.
Answer:
(i)  The pedigree analysis can be defined as the analysis of traits in several generations of a family. The
pedigree of Haemophilia, discovered by Haldane, in the descendants of Queen Victoria is a popular case
of such analysis.
(ii) The common Mendelian experiments are not possible in humans because
(a) Generation period is long.
(b) Progeny of a couple is small. 
7)
Name the host and the site where the following occur in the life cycle of a malarial parasite.
(i) Formation gametocytes
(ii) Fusion of gametocytes
OR
Briefly write the preventive measures for water and food borne diseases
  
Page 2


d o n e Biology - Sample Paper-8
1) A haeomophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
Answer:
Father  (Haemophilia); Mother XX (Normal homozygous)  So, the probability to have
haemophilic daughter will be 0%.
2) Differentiate between DNA and DNase.
Answer:
DNA is the deoxyribonucleic acid found in nucleus of a cell, while DNase is the catalytic enzyme used to cleave phosphodiester
linkage in the DNA.
3) Give the name of the causative agent of amoebiasis and write its any two symptoms.
Answer:
Entamoeba histolytica is a protozoan parasite in the large intestine of human. Symptoms include abdominal pain and cramps,
stool with excess mucous and blood clots.
4) Would you choose an exonuclease for producing recombinant DNA molecule?
Answer:
No, because exonuclease removes nucleotides from the terminal end (either 5' or 3') of DNA in one strand.
5) While doing a PCR, denaturation step is missed. What will be its effect on the process?
Answer:
If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template. No extension
will take place, hence no amplification will occur.
6) Why is pedigree analysis done in humans? List two reasons why the Mendelian experiments cannot be carried out in human
beings.
Answer:
(i)  The pedigree analysis can be defined as the analysis of traits in several generations of a family. The
pedigree of Haemophilia, discovered by Haldane, in the descendants of Queen Victoria is a popular case
of such analysis.
(ii) The common Mendelian experiments are not possible in humans because
(a) Generation period is long.
(b) Progeny of a couple is small. 
7)
Name the host and the site where the following occur in the life cycle of a malarial parasite.
(i) Formation gametocytes
(ii) Fusion of gametocytes
OR
Briefly write the preventive measures for water and food borne diseases
  
Methane 60 - 70%
(i) Red Blood Cells (RBCs) of human.  
(ii) Intestine of female Anopheles mosquito. 
OR
Preventive measures for water and food borne diseases are
(a) Consumption of clean drinking water, food, vegetable, fruits, etc.
(b) Washing hands before meals and after defecation.
(c) Proper disposal of waste and excreta.
(d) Cooking food throughly and keeping it at safe temperatue.
8) Define insertional inactivation. What is its significance?
Answer:
When a recombinant DNA is inserted into the coding sequence of enzyme beta galactosidase (P-gal), it results into the
inactivation of the enzyme, which is termed as insertional inactivation. It helps in the selection of recombinants.   
9) Why do people living in high altitude have more haemoglobin and high RBC count?
Answer:
This happens because at higher altitude the partial pressure of oxygen (atmospheric pressure) drops and sufficient oxygen is not
available. But gradually they are acclimatized or physiologically adapted and the symptoms of altitude sickness disappear by-
(a) Increase in the number of RBC- production.
(b) Decrease in binding capacity of haemoglobin.
(c) Increase in the breathing rate.
10) How do organisms manage with stressful conditions existing in their habitat for short duration?
Answer:
Organisms manage the stressful conditions in their habitat for short duration by the following
activities:
(a) Migration: It refers to the temporary movement of the organisms away from the stressful
conditions to a more hospitable area and return to their native habitat when stressful period is over.
Example: Birds from Siberia and other extremely cold regions migrate to Keoladeo National Park in
Bharatpur (Rajasthan).
(b) Suspending the Activities: Those animals, which are unable to migrate from the stressful
conditions avoid the stress by escaping in time.
Example: Hibernation of bear in winter or aestivation of snails in summer.
11) Define vegetative propagules and name any three of them with one example of each.
Answer:
In natural methods of propagation, a portion of the plant gets detached from the body of the mother plant. The detached portion
maybe a part of stem, leaf, root etc., which develops into a new independent plant under suitable environmental conditions.
These structures are called vegetative propagules.
Examples:
(a) Root - Sweet potato                           
(b) Stem - Potato
(c) Leaf ? BryophyHum
12) What is anaerobic digestion of wastewater?
Answer:
In anaerobic digestion of waste water bacteria present in anaerobic sludge digester which grow anaerobically digest bacteria &
fungi in the sluge. During the digestion, bacteria produces a mixture of gases such as -
Page 3


d o n e Biology - Sample Paper-8
1) A haeomophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
Answer:
Father  (Haemophilia); Mother XX (Normal homozygous)  So, the probability to have
haemophilic daughter will be 0%.
2) Differentiate between DNA and DNase.
Answer:
DNA is the deoxyribonucleic acid found in nucleus of a cell, while DNase is the catalytic enzyme used to cleave phosphodiester
linkage in the DNA.
3) Give the name of the causative agent of amoebiasis and write its any two symptoms.
Answer:
Entamoeba histolytica is a protozoan parasite in the large intestine of human. Symptoms include abdominal pain and cramps,
stool with excess mucous and blood clots.
4) Would you choose an exonuclease for producing recombinant DNA molecule?
Answer:
No, because exonuclease removes nucleotides from the terminal end (either 5' or 3') of DNA in one strand.
5) While doing a PCR, denaturation step is missed. What will be its effect on the process?
Answer:
If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template. No extension
will take place, hence no amplification will occur.
6) Why is pedigree analysis done in humans? List two reasons why the Mendelian experiments cannot be carried out in human
beings.
Answer:
(i)  The pedigree analysis can be defined as the analysis of traits in several generations of a family. The
pedigree of Haemophilia, discovered by Haldane, in the descendants of Queen Victoria is a popular case
of such analysis.
(ii) The common Mendelian experiments are not possible in humans because
(a) Generation period is long.
(b) Progeny of a couple is small. 
7)
Name the host and the site where the following occur in the life cycle of a malarial parasite.
(i) Formation gametocytes
(ii) Fusion of gametocytes
OR
Briefly write the preventive measures for water and food borne diseases
  
Methane 60 - 70%
(i) Red Blood Cells (RBCs) of human.  
(ii) Intestine of female Anopheles mosquito. 
OR
Preventive measures for water and food borne diseases are
(a) Consumption of clean drinking water, food, vegetable, fruits, etc.
(b) Washing hands before meals and after defecation.
(c) Proper disposal of waste and excreta.
(d) Cooking food throughly and keeping it at safe temperatue.
8) Define insertional inactivation. What is its significance?
Answer:
When a recombinant DNA is inserted into the coding sequence of enzyme beta galactosidase (P-gal), it results into the
inactivation of the enzyme, which is termed as insertional inactivation. It helps in the selection of recombinants.   
9) Why do people living in high altitude have more haemoglobin and high RBC count?
Answer:
This happens because at higher altitude the partial pressure of oxygen (atmospheric pressure) drops and sufficient oxygen is not
available. But gradually they are acclimatized or physiologically adapted and the symptoms of altitude sickness disappear by-
(a) Increase in the number of RBC- production.
(b) Decrease in binding capacity of haemoglobin.
(c) Increase in the breathing rate.
10) How do organisms manage with stressful conditions existing in their habitat for short duration?
Answer:
Organisms manage the stressful conditions in their habitat for short duration by the following
activities:
(a) Migration: It refers to the temporary movement of the organisms away from the stressful
conditions to a more hospitable area and return to their native habitat when stressful period is over.
Example: Birds from Siberia and other extremely cold regions migrate to Keoladeo National Park in
Bharatpur (Rajasthan).
(b) Suspending the Activities: Those animals, which are unable to migrate from the stressful
conditions avoid the stress by escaping in time.
Example: Hibernation of bear in winter or aestivation of snails in summer.
11) Define vegetative propagules and name any three of them with one example of each.
Answer:
In natural methods of propagation, a portion of the plant gets detached from the body of the mother plant. The detached portion
maybe a part of stem, leaf, root etc., which develops into a new independent plant under suitable environmental conditions.
These structures are called vegetative propagules.
Examples:
(a) Root - Sweet potato                           
(b) Stem - Potato
(c) Leaf ? BryophyHum
12) What is anaerobic digestion of wastewater?
Answer:
In anaerobic digestion of waste water bacteria present in anaerobic sludge digester which grow anaerobically digest bacteria &
fungi in the sluge. During the digestion, bacteria produces a mixture of gases such as -
20%
and 10% 
13) Why do internodal segments of sugarcane fail to propagate
vegetatively even when they are in contact with damp soil?
Answer:
On the stems, new buds develop from the nodes. So, for a vegetative reproduction of a plant through stem cutting should have at
least node. As intemodal segments of the sugarcane do not have nodes. Hence, they fail to propagate vegetatively even when
they are in contact with the damp soil. Amniocentesis is a technique by which genetic disorder in a developing foetus can be
detected. This is based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo.
14)
Describe the technique by which genetic disorder in a developing foetus can be detected.
OR
Describe three manners in which fertilisation of human ovum by a sperm can be prevented.
Answer:
Amniotic fluid contains cells and molecules shed by the foetus. The chromosomes of foetal cells can also
be used to find out the sex of the foetus and certain abnormalities. Thus, if an abnormality is found, the
mother can get the foetus aborted.
OR
Fertilisation of human ovum by a sperm can be prvented by the following methods.
(a) Condoms: They are barriers made of thin rubber/latex sheath and are used to cover the penis in the
male, or vagina and cervix in the female, just before coitus, so that the ejaculated semen would not enter
into the female reproductive tract.
'Nirodh' is a popular brand of condom for the male.
(b) Diaphragms, cervical caps and vaults'. They are also barriers made of rubber and 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.
(c) Spermicidal creams, jellies and foams are also used to kill the sperms.
15)
Explain the following terms with example.
(i) Codominance
(ii) Incomplete dominance
Answer:
(i) Codominance: It is the phenomenon of two different alleles of the same gene lacking
dominance-recessive relationship and expressing their effect simultaneously in the heterozygote.
Example: 'AB' type blood group is possible when allele 'A9 and 'B9 come together and express their
effect in -generation.
Incomplete dominance is the phenomenon where dominant allele do not completely express itself.
(ii) Incomplete dominance: It is the phenomenon where dominant allele do not completely express
itself.
Example, In Mirabili sjalapa (four 0' clock) & Antirrhinum majus (Snapdragon or dog flower), there
are two types of flower colour in pure state-red & white. When the two types of plants are crossed
the hybrid or plants of generation have pink flowers. If the latter are selfed, the plants
of generation are of three types-red, pink & white flowered in the ratio of 1:2:1.
Page 4


d o n e Biology - Sample Paper-8
1) A haeomophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
Answer:
Father  (Haemophilia); Mother XX (Normal homozygous)  So, the probability to have
haemophilic daughter will be 0%.
2) Differentiate between DNA and DNase.
Answer:
DNA is the deoxyribonucleic acid found in nucleus of a cell, while DNase is the catalytic enzyme used to cleave phosphodiester
linkage in the DNA.
3) Give the name of the causative agent of amoebiasis and write its any two symptoms.
Answer:
Entamoeba histolytica is a protozoan parasite in the large intestine of human. Symptoms include abdominal pain and cramps,
stool with excess mucous and blood clots.
4) Would you choose an exonuclease for producing recombinant DNA molecule?
Answer:
No, because exonuclease removes nucleotides from the terminal end (either 5' or 3') of DNA in one strand.
5) While doing a PCR, denaturation step is missed. What will be its effect on the process?
Answer:
If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template. No extension
will take place, hence no amplification will occur.
6) Why is pedigree analysis done in humans? List two reasons why the Mendelian experiments cannot be carried out in human
beings.
Answer:
(i)  The pedigree analysis can be defined as the analysis of traits in several generations of a family. The
pedigree of Haemophilia, discovered by Haldane, in the descendants of Queen Victoria is a popular case
of such analysis.
(ii) The common Mendelian experiments are not possible in humans because
(a) Generation period is long.
(b) Progeny of a couple is small. 
7)
Name the host and the site where the following occur in the life cycle of a malarial parasite.
(i) Formation gametocytes
(ii) Fusion of gametocytes
OR
Briefly write the preventive measures for water and food borne diseases
  
Methane 60 - 70%
(i) Red Blood Cells (RBCs) of human.  
(ii) Intestine of female Anopheles mosquito. 
OR
Preventive measures for water and food borne diseases are
(a) Consumption of clean drinking water, food, vegetable, fruits, etc.
(b) Washing hands before meals and after defecation.
(c) Proper disposal of waste and excreta.
(d) Cooking food throughly and keeping it at safe temperatue.
8) Define insertional inactivation. What is its significance?
Answer:
When a recombinant DNA is inserted into the coding sequence of enzyme beta galactosidase (P-gal), it results into the
inactivation of the enzyme, which is termed as insertional inactivation. It helps in the selection of recombinants.   
9) Why do people living in high altitude have more haemoglobin and high RBC count?
Answer:
This happens because at higher altitude the partial pressure of oxygen (atmospheric pressure) drops and sufficient oxygen is not
available. But gradually they are acclimatized or physiologically adapted and the symptoms of altitude sickness disappear by-
(a) Increase in the number of RBC- production.
(b) Decrease in binding capacity of haemoglobin.
(c) Increase in the breathing rate.
10) How do organisms manage with stressful conditions existing in their habitat for short duration?
Answer:
Organisms manage the stressful conditions in their habitat for short duration by the following
activities:
(a) Migration: It refers to the temporary movement of the organisms away from the stressful
conditions to a more hospitable area and return to their native habitat when stressful period is over.
Example: Birds from Siberia and other extremely cold regions migrate to Keoladeo National Park in
Bharatpur (Rajasthan).
(b) Suspending the Activities: Those animals, which are unable to migrate from the stressful
conditions avoid the stress by escaping in time.
Example: Hibernation of bear in winter or aestivation of snails in summer.
11) Define vegetative propagules and name any three of them with one example of each.
Answer:
In natural methods of propagation, a portion of the plant gets detached from the body of the mother plant. The detached portion
maybe a part of stem, leaf, root etc., which develops into a new independent plant under suitable environmental conditions.
These structures are called vegetative propagules.
Examples:
(a) Root - Sweet potato                           
(b) Stem - Potato
(c) Leaf ? BryophyHum
12) What is anaerobic digestion of wastewater?
Answer:
In anaerobic digestion of waste water bacteria present in anaerobic sludge digester which grow anaerobically digest bacteria &
fungi in the sluge. During the digestion, bacteria produces a mixture of gases such as -
20%
and 10% 
13) Why do internodal segments of sugarcane fail to propagate
vegetatively even when they are in contact with damp soil?
Answer:
On the stems, new buds develop from the nodes. So, for a vegetative reproduction of a plant through stem cutting should have at
least node. As intemodal segments of the sugarcane do not have nodes. Hence, they fail to propagate vegetatively even when
they are in contact with the damp soil. Amniocentesis is a technique by which genetic disorder in a developing foetus can be
detected. This is based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo.
14)
Describe the technique by which genetic disorder in a developing foetus can be detected.
OR
Describe three manners in which fertilisation of human ovum by a sperm can be prevented.
Answer:
Amniotic fluid contains cells and molecules shed by the foetus. The chromosomes of foetal cells can also
be used to find out the sex of the foetus and certain abnormalities. Thus, if an abnormality is found, the
mother can get the foetus aborted.
OR
Fertilisation of human ovum by a sperm can be prvented by the following methods.
(a) Condoms: They are barriers made of thin rubber/latex sheath and are used to cover the penis in the
male, or vagina and cervix in the female, just before coitus, so that the ejaculated semen would not enter
into the female reproductive tract.
'Nirodh' is a popular brand of condom for the male.
(b) Diaphragms, cervical caps and vaults'. They are also barriers made of rubber and 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.
(c) Spermicidal creams, jellies and foams are also used to kill the sperms.
15)
Explain the following terms with example.
(i) Codominance
(ii) Incomplete dominance
Answer:
(i) Codominance: It is the phenomenon of two different alleles of the same gene lacking
dominance-recessive relationship and expressing their effect simultaneously in the heterozygote.
Example: 'AB' type blood group is possible when allele 'A9 and 'B9 come together and express their
effect in -generation.
Incomplete dominance is the phenomenon where dominant allele do not completely express itself.
(ii) Incomplete dominance: It is the phenomenon where dominant allele do not completely express
itself.
Example, In Mirabili sjalapa (four 0' clock) & Antirrhinum majus (Snapdragon or dog flower), there
are two types of flower colour in pure state-red & white. When the two types of plants are crossed
the hybrid or plants of generation have pink flowers. If the latter are selfed, the plants
of generation are of three types-red, pink & white flowered in the ratio of 1:2:1.
16)
(i) You are given tall pea plants with yellow seeds, whose genotypes are unknown. How would you
find the genotype of these plants? Explain with the help of cross.
(ii) Identify A, B and C in the table given below.
Pattern in Inheritance Monohybrid Phenotypic
Codominance A?
B? Progeny resembled only one of the parents
Incomplete dominance C?
Answer:
(i)  The given tall pea plant with yellow seeds need to be crossed with a dwarf plant with green seeds. 
 In this cross, the -generation shows four phenotypes in the ratio of 1 : 1 : 1 :
1. So, the given plant is heterozygous for both the traits.       (ii) A - Dominant trait B-Dominance C - Phenotype obtained in
between of two parental traits.
17) Study the figure given below and answer the following questions. 
(i) Name the molecule 'X' synthesised by 'i' gene. How does this molecule get inactivated?
(ii) Which one of the structural genes codes for p-galactosidase?
(iii) When will the transcription of this gene stop?
Answer:
(i)  Molecule 'X' is a represser protein. When an inducer combines with it, it is inactivated. 
(ii) 'z' gene.     
(iii) Transcription of Gene Stops
(a) In the case when substrate (lactose) is not available.
(b) Energy source, (glucose) is available to the cells.
18) Write a short note on detection of cancer.
Answer:
Cancer detection is considered to be the first step towards treatment. Its early detection is essential for its cure. Some of the
ways to detect cancer are Biopsy: A piece of the suspected tissue cut into thin section is stained and examined under
microscope. MRI (Magnetic Resonance Imaging): It uses strong magnetic fields and non-ionising radiations to accurately detect
pathological changes in the living tissue.  Antibodies against cancer-specific antigens are also used for the detection of certain
cancers. 
19)
The outline structure of a drug is given below.
OR
Page 5


d o n e Biology - Sample Paper-8
1) A haeomophilic man marries a normal homozygous woman. What is the probability that their daughter will be haemophilic?
Answer:
Father  (Haemophilia); Mother XX (Normal homozygous)  So, the probability to have
haemophilic daughter will be 0%.
2) Differentiate between DNA and DNase.
Answer:
DNA is the deoxyribonucleic acid found in nucleus of a cell, while DNase is the catalytic enzyme used to cleave phosphodiester
linkage in the DNA.
3) Give the name of the causative agent of amoebiasis and write its any two symptoms.
Answer:
Entamoeba histolytica is a protozoan parasite in the large intestine of human. Symptoms include abdominal pain and cramps,
stool with excess mucous and blood clots.
4) Would you choose an exonuclease for producing recombinant DNA molecule?
Answer:
No, because exonuclease removes nucleotides from the terminal end (either 5' or 3') of DNA in one strand.
5) While doing a PCR, denaturation step is missed. What will be its effect on the process?
Answer:
If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template. No extension
will take place, hence no amplification will occur.
6) Why is pedigree analysis done in humans? List two reasons why the Mendelian experiments cannot be carried out in human
beings.
Answer:
(i)  The pedigree analysis can be defined as the analysis of traits in several generations of a family. The
pedigree of Haemophilia, discovered by Haldane, in the descendants of Queen Victoria is a popular case
of such analysis.
(ii) The common Mendelian experiments are not possible in humans because
(a) Generation period is long.
(b) Progeny of a couple is small. 
7)
Name the host and the site where the following occur in the life cycle of a malarial parasite.
(i) Formation gametocytes
(ii) Fusion of gametocytes
OR
Briefly write the preventive measures for water and food borne diseases
  
Methane 60 - 70%
(i) Red Blood Cells (RBCs) of human.  
(ii) Intestine of female Anopheles mosquito. 
OR
Preventive measures for water and food borne diseases are
(a) Consumption of clean drinking water, food, vegetable, fruits, etc.
(b) Washing hands before meals and after defecation.
(c) Proper disposal of waste and excreta.
(d) Cooking food throughly and keeping it at safe temperatue.
8) Define insertional inactivation. What is its significance?
Answer:
When a recombinant DNA is inserted into the coding sequence of enzyme beta galactosidase (P-gal), it results into the
inactivation of the enzyme, which is termed as insertional inactivation. It helps in the selection of recombinants.   
9) Why do people living in high altitude have more haemoglobin and high RBC count?
Answer:
This happens because at higher altitude the partial pressure of oxygen (atmospheric pressure) drops and sufficient oxygen is not
available. But gradually they are acclimatized or physiologically adapted and the symptoms of altitude sickness disappear by-
(a) Increase in the number of RBC- production.
(b) Decrease in binding capacity of haemoglobin.
(c) Increase in the breathing rate.
10) How do organisms manage with stressful conditions existing in their habitat for short duration?
Answer:
Organisms manage the stressful conditions in their habitat for short duration by the following
activities:
(a) Migration: It refers to the temporary movement of the organisms away from the stressful
conditions to a more hospitable area and return to their native habitat when stressful period is over.
Example: Birds from Siberia and other extremely cold regions migrate to Keoladeo National Park in
Bharatpur (Rajasthan).
(b) Suspending the Activities: Those animals, which are unable to migrate from the stressful
conditions avoid the stress by escaping in time.
Example: Hibernation of bear in winter or aestivation of snails in summer.
11) Define vegetative propagules and name any three of them with one example of each.
Answer:
In natural methods of propagation, a portion of the plant gets detached from the body of the mother plant. The detached portion
maybe a part of stem, leaf, root etc., which develops into a new independent plant under suitable environmental conditions.
These structures are called vegetative propagules.
Examples:
(a) Root - Sweet potato                           
(b) Stem - Potato
(c) Leaf ? BryophyHum
12) What is anaerobic digestion of wastewater?
Answer:
In anaerobic digestion of waste water bacteria present in anaerobic sludge digester which grow anaerobically digest bacteria &
fungi in the sluge. During the digestion, bacteria produces a mixture of gases such as -
20%
and 10% 
13) Why do internodal segments of sugarcane fail to propagate
vegetatively even when they are in contact with damp soil?
Answer:
On the stems, new buds develop from the nodes. So, for a vegetative reproduction of a plant through stem cutting should have at
least node. As intemodal segments of the sugarcane do not have nodes. Hence, they fail to propagate vegetatively even when
they are in contact with the damp soil. Amniocentesis is a technique by which genetic disorder in a developing foetus can be
detected. This is based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo.
14)
Describe the technique by which genetic disorder in a developing foetus can be detected.
OR
Describe three manners in which fertilisation of human ovum by a sperm can be prevented.
Answer:
Amniotic fluid contains cells and molecules shed by the foetus. The chromosomes of foetal cells can also
be used to find out the sex of the foetus and certain abnormalities. Thus, if an abnormality is found, the
mother can get the foetus aborted.
OR
Fertilisation of human ovum by a sperm can be prvented by the following methods.
(a) Condoms: They are barriers made of thin rubber/latex sheath and are used to cover the penis in the
male, or vagina and cervix in the female, just before coitus, so that the ejaculated semen would not enter
into the female reproductive tract.
'Nirodh' is a popular brand of condom for the male.
(b) Diaphragms, cervical caps and vaults'. They are also barriers made of rubber and 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.
(c) Spermicidal creams, jellies and foams are also used to kill the sperms.
15)
Explain the following terms with example.
(i) Codominance
(ii) Incomplete dominance
Answer:
(i) Codominance: It is the phenomenon of two different alleles of the same gene lacking
dominance-recessive relationship and expressing their effect simultaneously in the heterozygote.
Example: 'AB' type blood group is possible when allele 'A9 and 'B9 come together and express their
effect in -generation.
Incomplete dominance is the phenomenon where dominant allele do not completely express itself.
(ii) Incomplete dominance: It is the phenomenon where dominant allele do not completely express
itself.
Example, In Mirabili sjalapa (four 0' clock) & Antirrhinum majus (Snapdragon or dog flower), there
are two types of flower colour in pure state-red & white. When the two types of plants are crossed
the hybrid or plants of generation have pink flowers. If the latter are selfed, the plants
of generation are of three types-red, pink & white flowered in the ratio of 1:2:1.
16)
(i) You are given tall pea plants with yellow seeds, whose genotypes are unknown. How would you
find the genotype of these plants? Explain with the help of cross.
(ii) Identify A, B and C in the table given below.
Pattern in Inheritance Monohybrid Phenotypic
Codominance A?
B? Progeny resembled only one of the parents
Incomplete dominance C?
Answer:
(i)  The given tall pea plant with yellow seeds need to be crossed with a dwarf plant with green seeds. 
 In this cross, the -generation shows four phenotypes in the ratio of 1 : 1 : 1 :
1. So, the given plant is heterozygous for both the traits.       (ii) A - Dominant trait B-Dominance C - Phenotype obtained in
between of two parental traits.
17) Study the figure given below and answer the following questions. 
(i) Name the molecule 'X' synthesised by 'i' gene. How does this molecule get inactivated?
(ii) Which one of the structural genes codes for p-galactosidase?
(iii) When will the transcription of this gene stop?
Answer:
(i)  Molecule 'X' is a represser protein. When an inducer combines with it, it is inactivated. 
(ii) 'z' gene.     
(iii) Transcription of Gene Stops
(a) In the case when substrate (lactose) is not available.
(b) Energy source, (glucose) is available to the cells.
18) Write a short note on detection of cancer.
Answer:
Cancer detection is considered to be the first step towards treatment. Its early detection is essential for its cure. Some of the
ways to detect cancer are Biopsy: A piece of the suspected tissue cut into thin section is stained and examined under
microscope. MRI (Magnetic Resonance Imaging): It uses strong magnetic fields and non-ionising radiations to accurately detect
pathological changes in the living tissue.  Antibodies against cancer-specific antigens are also used for the detection of certain
cancers. 
19)
The outline structure of a drug is given below.
OR
(i) Which group of drugs does this represent?
(ii) What are the modes of consumption of these drugs?
(iii) Name the organ of the body which is affected by consumption of these drugs.
Answer:
(i)  Cannabinoids (e.g. Bhang, charas, hashish, marijuana, etc.)
(ii) The mode of consumption is inhalation or oral ingestion.
(iii) Organs affected are heart and cardiovascular system. Such drugs cause illusions delusions
(hallucinations) and change the feelings or perception.
20)
Draw a schematic sketch of pBR322 plasmid and label the following in it.
(i) Any two restriction sites
(ii) Ori and rop genes
(iii) Any two antibiotic resistant genes
Answer:
21) What is a bioreactor? Why is it used in biotechnology?
Answer:
Small volume cultures cannot yield appreciable quantities of products. In order to have larger quantities, bioreactors have been
developed. Abioreactor provides the optimal conditions substrate, salts, vitamins and oxygen. Bioreactors are used in
biotechnology as
(a) In industrial biotechnology for the production of fermented foods, wine, organic acids, etc.
(b) It may also be used in environment biotechnology to treat sewage and waste water.
(c) Used for the production of recombinant product.
(d) Bioreactors are also used in the pharmaceutical industry for the growth of specialised pure cultures of
bacteria, fungi, yeast and the production of enzyme, drugs, etc.
22) Name important defense mechanisms in plants against herbivory.
Answer:
(a) The herbivores are predators for plants. The insects are phytophagus (feeding on plants). So, the plants show morphological
as well as chemical defense against herbivores, e.g., thorns of rose and Acacia as well as cactus.  (b) Certain plants produce
chemicals, such as opium, quinine, caffeine, nicotine, etc., to protect them against being grazed by the animals. (c) Calotropis
produces highly poisonous cardiac glycosides. So, the cattle and goats do not eat this plant.