CBSE Class 12 Biology 2024 question paper (57/1)

Maximum marks 70 · Time 3 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

1 mark each

Q.11 mark $In which of the following plants are both male and female flowers born on the same plant and the mode of pollination can be geitonogamy or xenogamy ?$
Tap an option to check your answer.
Q.21 mark $Which one of the following hormones is secreted by the human placenta that helps in the maintenance of pregnancy ?$
Tap an option to check your answer.
Q.31 mark $The periodic abstinence by a couple for family planning should be from :$
Tap an option to check your answer.
Q.41 mark $Select the incorrect match from the following : Human Karyotype - Characters$
Tap an option to check your answer.
Q.51 mark $You know that there are twenty different types of naturally occurring amino acids and four different types of bases in the DNA. A combination of 3 such bases code for a specific amino acid. If instead there are 96 different amino acids and 12 different bases in the DNA, then the minimum number of combination of bases required to form a codon is :$
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Q.61 mark $The type of bond represented by the dotted line '-----' in a schematic polynucleotide chain is :$
Tap an option to check your answer.
Q.71 mark $In which of the following conditions/diseases is there a substantial increase in the activity of mast cells observed in the human body ?$
Tap an option to check your answer.
Q.81 mark $Lactobacillus that sets milk into curd is categorised as :$
Tap an option to check your answer.
Q.91 mark $Which one of the following transgenic animals is being used to test the safety of the polio vaccine ?$
Tap an option to check your answer.
Q.101 mark $Restriction Endonuclease - Hind II always cuts DNA molecules at a particular point by recognising a specific sequence of :$
Tap an option to check your answer.
Q.111 mark $The improved trait that is found in the genetically modified transgenic crop - Golden rice is :$
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Q.121 mark $The rate of formation of new organic matter by consumers, and the biomass available for consumption of herbivores as well as decomposers are referred to as :$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : The laws of our country permit legal adoption and it is as yet, one of the best methods for childless couples looking for parenthood. Reason (R) : Emotional, religious and social factors are no deterrents to the legal adoption of orphaned and destitute children in India.$
Tap an option to check your answer.
Q.141 mark $\text{F}_2$
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Q.151 mark $Assertion (A) : Agrobacterium tumefaciens is a pathogen of several monocot plants. Reason (R) : It is able to deliver a piece of DNA known as 'T-DNA' to transform normal plant cells into a tumor.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Indian Government has set up an organisation known as GEAC to decide the validity of GM research. Reason (R) : Genetic modification of organisms has no effect when such organisms are introduced in the ecosystem.$
Tap an option to check your answer.

Section B

2 marks each

Q.172 marks $Identify A, B, C and D in the table given below : Terms Part of the plant it represents Pericarp'A''B' Cotyledon in seed of grass family Embryonal axis'C''D' Remains of nucellus in a seed$
Q.182 marks $Observe the picture given below. Name the naturalist and write the explanation given by him that evolution of life forms had occurred on the basis of this example.$
Q.192 marks $Write the basic steps followed in the Assisted Reproductive Technologies (ART) programme to help childless couples. Why is it also known as test tube baby programme ?$
Q.20 (a)2 marks $A farmer while working on his farm was bitten by a poisonous snake. He was rushed to a nearby health centre where the doctor gave him an injection to save his life. (i) What did the doctor inject and why ? (ii) Name the kind of immunity provided by this injection.$
OR
Q.20 (b)2 marks $Why do organic farmers not recommend complete eradication of insect pests ? Explain giving reason.$
Q.212 marks $Study the diagram of a pyramid of biomass given below. Name the two standing crops that could be occupying level 'A' and level 'B' in it. Name this type of pyramid and the ecosystem in which it is found.$

Terms	Part of the plant it represents
Pericarp	'A'
'B'	Cotyledon in seed of grass family
Embryonal axis	'C'
'D'	Remains of nucellus in a seed

Section C

3 marks each

Q.223 marks $Explain the mode of action of contraceptive pills taken by human females. Mention the schedule to be followed for effective outcome.$
Q.233 marks $(a) Name and write two characteristics of the type of DNA that forms the basis of DNA fingerprinting technique. (b) Mention any two applications of this technique.$
Q.243 marks $(a) Explain the significance of the experiment carried out by S.L. Miller. Name the scientists whose hypothesis prompted him to carry out this experiment. (b) How does meteorite analysis favour this hypothesis ?$

Q.253 marks

Identify A, B, C, D, E and F in the table given below : Name of Human Disease Causative Organism Symptoms Pneumonia Streptococcus'A' Typhoid'B' High fever, weakness, headache, stomach pain Common Cold Rhino virus'C' Ringworm'D' Dry scaly lesions on body parts, redness, itching Ascariasis Ascaris'E''F' Entamoeba histolytica Constipation, cramps, stools with mucous and blood clots

Q.263 marks $In a family, the father, the daughter and the son are colour blind, whereas the mother has normal vision. Do you think the son and the daughter have inherited the disease from their father ? Work out a cross to justify your answer.$
Q.27 (a)3 marks $(i) What are transgenic animals ? (ii) Name the first transgenic cow and state its importance.$
OR
Q.27 (b)3 marks $(i) Explain the convention for naming EcoRI. (ii) With the help of an illustration only, show the action of EcoRI on a DNA Polynucleotide.$
Q.283 marks $(a) Explain how it is ensured that the orchid Ophrys is pollinated by a specific species of bee. (b) Describe co-evolution with the help of this example.$

Name of Human Disease	Causative Organism	Symptoms
Pneumonia	Streptococcus	'A'
Typhoid	'B'	High fever, weakness, headache, stomach pain
Common Cold	Rhino virus	'C'
Ringworm	'D'	Dry scaly lesions on body parts, redness, itching
Ascariasis	Ascaris	'E'
'F'	Entamoeba histolytica	Constipation, cramps, stools with mucous and blood clots

Section D

Isn't it incredible that India's land area is only $2{\cdot}4$ per cent of the world's total land area whereas its share of the global species diversity is an impressive $8{\cdot}1$ per cent ! However, in these estimates of species, prokaryotes do not figure anywhere. Biologists are always keen on collecting data with respect to species diversity observed in different regions of the world. The data collected based on the survey conducted for species richness of groups of mammals in three different regions of the world is shown in the bar graph given below :
Q.29 (a)1 mark $Why is the species richness maximum in Region III in the bar graph ?$
OR
Q.29 (a) OR1 mark $Why is the species richness minimum in Region I in the bar graph ?$
Q.29 (b)1 mark $Plants and animals do not have uniform diversity in the world but show rather uneven distribution. Mention what this kind of diversity is referred to as.$
Q.29 (c)2 marks $Why is it that prokaryotes do not have an estimated number of their species diversity as seen in plants and animals ? Explain.$
Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow :
Q.30 (a)1 mark $Identify the colony that has got transformed. Justify your answer.$
Q.30 (b)2 marks $What are the sites in a plasmid called where ampicillin and tetracycline resistance genes are inserted ? State their role in genetic engineering.$
Q.30 (c)1 mark $Name two enzymes playing an important role in genetic engineering.$
OR
Q.30 (c) OR1 mark $\beta$

Section E

5 marks each

Q.31 (a)5 marks $(i) Explain the development of male gametophyte in an angiosperm. (ii) Draw a labelled diagram of a three-celled male gametophyte.$
OR
Q.31 (b)5 marks $(i) Draw a diagrammatic sectional view of ovary of human female and label the following : (1) Blood vessels (2) Primary follicle (3) Tertiary follicle (4) Ovum (ii) At which stage of life are primary follicles formed in a human female ? (iii) Explain the events (both hormonal and structural) that occur at the time of ovulation till the onset of the next menstrual cycle.$
Q.32 (a)5 marks $Stability, as one of the properties of genetic material, was very evident in one of the very early experiments in genetics. Name the scientist and describe his experiment. State the conclusion he arrived at.$
OR
Q.32 (b)5 marks $A tall pea plant bearing violet flowers with unknown genotype is given. Find the genotype by working out different crosses only by selfing the plants. Write the genotypic and phenotypic ratios of each cross shown by you.$
Q.33 (a)5 marks $(i) Name and explain the property present in normal cells but is lost in cancer cells. (ii) All normal human cells have genes that may become cancerous under certain conditions. Name them and explain how. (iii) State the role of the following techniques in detection and diagnosis of cancer : (1) Biopsy and Histopathology (2) Magnetic Resonance Imaging$
OR
Q.33 (b)5 marks $\downarrow$

Section A

1 mark each

Q.11 mark $The type of bond represented by the dotted line '-----' in a schematic polynucleotide chain is :$
Tap an option to check your answer.
Q.21 mark $Select the option that has the correct sequence of events of human female reproductive cycle : (i) Secretion of FSH (ii) Ovulation (iii) Growth of corpus luteum (iv) Growth of follicle and oogenesis (v) Sudden increase in LH Options :$
Tap an option to check your answer.
Q.31 mark $Lactobacillus that sets milk into curd is categorised as :$
Tap an option to check your answer.
Q.41 mark $The specific Bt toxin genes which protect the cotton plants against the cotton bollworms are :$
Tap an option to check your answer.
Q.51 mark $Listed below are some amino acids and their corresponding mRNA codons : Amino acid mRNA codons Phenylalanine UUU Lysine AAG Arginine CGA Alanine GCA Select the DNA sequence that would code for the following polypeptide sequence : Polypeptide : Alanine - Arginine - Lysine - Phenylalanine$
Tap an option to check your answer.
Q.61 mark $In which of the following plants are both male and female flowers born on the same plant and the mode of pollination can be geitonogamy or xenogamy ?$
Tap an option to check your answer.
Q.71 mark $Which one of the following transgenic animals is being used to test the safety of the polio vaccine ?$
Tap an option to check your answer.
Q.81 mark $In which of the following conditions/diseases is there a substantial increase in the activity of mast cells observed in the human body ?$
Tap an option to check your answer.
Q.91 mark $The periodic abstinence by a couple for family planning should be from :$
Tap an option to check your answer.
Q.101 mark $Select the incorrect match from the following : Human Karyotype - Characters$
Tap an option to check your answer.
Q.111 mark $Using a DNA template, how many new DNA molecules would be generated after 10 cycles of amplification in PCR ?$
Tap an option to check your answer.
Q.121 mark $Read the four statements given below and select the option having two correct statements : (i) A lion eating a deer and a sparrow feeding on grains are ecologically similar in being consumers. (ii) Predator starfish Pisaster helps in maintaining species diversity of some invertebrates. (iii) Predators ultimately lead to extinction of prey species. (iv) Production of chemicals nicotine and strychnine by plants are metabolic disorders.$
Tap an option to check your answer.
For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : Agrobacterium tumefaciens is a pathogen of several monocot plants. Reason (R) : It is able to deliver a piece of DNA known as 'T-DNA' to transform normal plant cells into a tumor.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : The laws of our country permit legal adoption and it is as yet, one of the best methods for childless couples looking for parenthood. Reason (R) : Emotional, religious and social factors are no deterrents to the legal adoption of orphaned and destitute children in India.$
Tap an option to check your answer.
Q.151 mark $\text{F}_2$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Functional ADA cDNA genes must be inserted in the lymphocytes at the early embryonic stage in gene therapy for ADA deficiency. Reason (R) : Cells in the embryonic stage are immortal, differentiated and easy to manipulate.$
Tap an option to check your answer.

Amino acid	mRNA codons
Phenylalanine	UUU
Lysine	AAG
Arginine	CGA
Alanine	GCA

Section B

2 marks each

Q.172 marks $Do you think apomixis can be compared to asexual reproduction ? Justify your answer. State the benefits of apomixis to the farmers.$
Q.18 (a)2 marks $A farmer while working on his farm was bitten by a poisonous snake. He was rushed to a nearby health centre where the doctor gave him an injection to save his life. (i) What did the doctor inject and why ? (ii) Name the kind of immunity provided by this injection.$
OR
Q.18 (b)2 marks $Why do organic farmers not recommend complete eradication of insect pests ? Explain giving reason.$
Q.192 marks $Observe the picture given below. Name the naturalist and write the explanation given by him that evolution of life forms had occurred on the basis of this example.$
Q.202 marks $Write the basic steps followed in the Assisted Reproductive Technologies (ART) programme to help childless couples. Why is it also known as test tube baby programme ?$
Q.212 marks $A specific plant species was introduced into Australia in 1920 and later it became invasive spreading over millions of hectares of rangeland. (a) Name the plant that was introduced into Australia and mention the reason for its uncontrollable growth. (b) State how its spread was eventually brought under control.$

Section C

3 marks each

Q.22 (a)3 marks $(i) What are transgenic animals ? (ii) Name the first transgenic cow and state its importance.$
OR
Q.22 (b)3 marks $(i) Explain the convention for naming EcoRI. (ii) With the help of an illustration only, show the action of EcoRI on a DNA Polynucleotide.$

Q.233 marks

Identify A, B, C, D, E and F in the table given below : Name of Human Disease Causative Organism Symptoms Pneumonia Streptococcus'A' Typhoid'B' High fever, weakness, headache, stomach pain Common cold Rhino virus'C' Ringworm'D' Dry scaly lesions on body parts, redness, itching Ascariasis Ascaris'E''F' Entamoeba histolytica Constipation, cramps, stools with mucous and blood clots

Q.243 marks $Explain the mode of action of contraceptive pills taken by human females. Mention the schedule to be followed for effective outcome.$
Q.253 marks $(a) Name and write two characteristics of the type of DNA that forms the basis of DNA fingerprinting technique. (b) Mention any two applications of this technique.$
Q.263 marks $Given below is a picture that shows the magnified blood smear of a patient under a microscope. (a) Name the disease the blood smear is indicative of. Write the symptoms of the disease and its cause. (b) Explain the inheritance pattern of the disease with the help of a suitable cross.$
Q.273 marks $(a) Explain the significance of the experiment carried out by S.L. Miller. Name the scientists whose hypothesis prompted him to carry out this experiment. (b) How does meteorite analysis favour this hypothesis ?$
Q.283 marks $(a) State what is primary productivity and mention its units. (b) Some ecologists observed that primary productivity of a place in Rajasthan was low as compared to a particular place in Kerala. Explain why.$

Name of Human Disease	Causative Organism	Symptoms
Pneumonia	Streptococcus	'A'
Typhoid	'B'	High fever, weakness, headache, stomach pain
Common cold	Rhino virus	'C'
Ringworm	'D'	Dry scaly lesions on body parts, redness, itching
Ascariasis	Ascaris	'E'
'F'	Entamoeba histolytica	Constipation, cramps, stools with mucous and blood clots

Section D

Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow :
Q.29 (a)1 mark $Identify the colony that has got transformed. Justify your answer.$
Q.29 (b)2 marks $What are the sites in a plasmid called where ampicillin and tetracycline resistance genes are inserted ? State their role in genetic engineering.$
Q.29 (c)1 mark $Name two enzymes playing an important role in genetic engineering.$
OR
Q.29 (c) OR1 mark $\beta$
Isn't it incredible that India's land area is only $2{\cdot}4$ per cent of the world's total land area whereas its share of the global species diversity is an impressive $8{\cdot}1$ per cent ! However, in these estimates of species, prokaryotes do not figure anywhere. Biologists are always keen on collecting data with respect to species diversity observed in different regions of the world. The data collected based on the survey conducted for species richness of groups of mammals in three different regions of the world is shown in the bar graph given below :
Q.30 (a)1 mark $Why is the species richness maximum in Region III in the bar graph ?$
OR
Q.30 (a) OR1 mark $Why is the species richness minimum in Region I in the bar graph ?$
Q.30 (b)1 mark $Plants and animals do not have uniform diversity in the world but show rather uneven distribution. Mention what this kind of diversity is referred to as.$
Q.30 (c)2 marks $Why is it that prokaryotes do not have an estimated number of their species diversity as seen in plants and animals ? Explain.$

Section E

5 marks each

Q.31 (a)5 marks $(i) Name and explain the property present in normal cells but is lost in cancer cells. (ii) All normal human cells have genes that may become cancerous under certain conditions. Name them and explain how. (iii) State the role of the following techniques in detection and diagnosis of cancer : (1) Biopsy and Histopathology (2) Magnetic Resonance Imaging$
OR
Q.31 (b)5 marks $\downarrow$
Q.32 (a)5 marks $Many patterns of inheritance deviate considerably from the pattern of inheritance as explained by Mendel. List any four such inheritance patterns and explain any three with the help of an example each.$
OR
Q.32 (b)5 marks $(i) Construct a transcription unit with a coding strand given below with proper labelling : A T G C T G A T G C G A (ii) When does a coding strand become a template strand ? (iii) Why does a double-helix DNA molecule transcribe into a single-stranded RNA molecule ?$
Q.33 (a)5 marks $(i) Explain the development of male gametophyte in an angiosperm. (ii) Draw a labelled diagram of a three-celled male gametophyte.$
OR
Q.33 (b)5 marks $(i) Draw a diagrammatic sectional view of ovary of human female and label the following : (1) Blood vessels (2) Primary follicle (3) Tertiary follicle (4) Ovum (ii) At which stage of life are primary follicles formed in a human female ? (iii) Explain the events (both hormonal and structural) that occur at the time of ovulation till the onset of the next menstrual cycle.$

Section A

1 mark each

Q.11 mark $Refer to the Venn diagram given below. Select the option with correct examples P, Q, and R :$
Tap an option to check your answer.
Q.21 mark $The type of bond represented by the dotted line '-----' in a schematic polynucleotide chain is :$
Tap an option to check your answer.
Q.31 mark $Lactobacillus that sets milk into curd is categorised as :$
Tap an option to check your answer.
Q.41 mark $Which one of the following transgenic animals is being used to test the safety of the polio vaccine ?$
Tap an option to check your answer.
Q.51 mark $The scientist who proposed that "embryos of all vertebrates including humans develop a row of vestigial gill slits behind the head but it is a functional organ only in fish and replaced by lungs in all other vertebrates" is :$
Tap an option to check your answer.
Q.61 mark $Which one of the following hormones is secreted by the human placenta that helps in the maintenance of pregnancy ?$
Tap an option to check your answer.
Q.71 mark $During an allergic reaction, the binding of antigen to IgE antibodies initiates release of :$
Tap an option to check your answer.
Q.81 mark $Select the incorrect match from the following : Human Karyotype - Characters$
Tap an option to check your answer.
Q.91 mark $Restriction Endonuclease - Hind II always cuts DNA molecules at a particular point by recognising a specific sequence of :$
Tap an option to check your answer.
Q.101 mark $The periodic abstinence by a couple for family planning should be from :$
Tap an option to check your answer.
Q.111 mark $Which one of the following bacteria were used by Stanley Cohen and Herbert Boyer to accomplish the construction of the first rDNA ?$
Tap an option to check your answer.
Q.121 mark $The organism that occupies more than one trophic level in a pond ecosystem is :$
Tap an option to check your answer.
For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : Indian Government has set up an organisation known as GEAC to decide the validity of GM research. Reason (R) : Genetic modification of organisms has no effect when such organisms are introduced in the ecosystem.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : Gene flow increases genetic variations. Reason (R) : The random introduction of new alleles into a recipient population and their removal from donor population affects allele frequency.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : The laws of our country permit legal adoption and it is as yet, one of the best methods for childless couples looking for parenthood. Reason (R) : Emotional, religious and social factors are no deterrents to the legal adoption of orphaned and destitute children in India.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Agrobacterium tumefaciens is a pathogen of several monocot plants. Reason (R) : It is able to deliver a piece of DNA known as 'T-DNA' to transform normal plant cells into a tumor.$
Tap an option to check your answer.

Section B

2 marks each

Q.172 marks $Study the diagram of a pyramid of biomass given below. Name the two standing crops that could be occupying level 'A' and level 'B' in it. Name this type of pyramid and the ecosystem in which it is found.$
Q.182 marks $Given below is an illustration of the experiment performed by Louis Pasteur. Explain the experiment and its conclusion.$
Q.192 marks $Identify A, B, C and D in the table given below : Terms Part of the plant it represents Pericarp'A''B' Cotyledon in seed of grass family Embryonal axis'C''D' Remains of nucellus in a seed$
Q.20 (a)2 marks $"Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used." Support this statement with the help of two suitable examples.$
OR
Q.20 (b)2 marks $Identify A, B, C and D in the following table : Scientific name of source plant Drug Harmful effects / Body part affected 1. Papaver somniferum A Depressant/slows down body functions 2. Cannabis sativa B C 3. Erythroxylum coca Cocaine D$
Q.212 marks $Write the basic steps followed in the Assisted Reproductive Technologies (ART) programme to help childless couples. Why is it also known as test tube baby programme ?$

Terms	Part of the plant it represents
Pericarp	'A'
'B'	Cotyledon in seed of grass family
Embryonal axis	'C'
'D'	Remains of nucellus in a seed

Scientific name of source plant	Drug	Harmful effects / Body part affected
1. Papaver somniferum	A	Depressant/slows down body functions
2. Cannabis sativa	B	C
3. Erythroxylum coca	Cocaine	D

Section C

3 marks each

Q.223 marks $(a) Explain the significance of the experiment carried out by S.L. Miller. Name the scientists whose hypothesis prompted him to carry out this experiment. (b) How does meteorite analysis favour this hypothesis ?$
Q.233 marks $(a) Identify the picture given below and name the tool under which it was viewed. (b) What do the dark spots represent in the picture ? Explain how and why are they formed.$
Q.243 marks $In a family, the father, the daughter and the son are colour blind, whereas the mother has normal vision. Do you think the son and the daughter have inherited the disease from their father ? Work out a cross to justify your answer.$
Q.253 marks $Identify A and B in the diagram below. Explain their role in the immune system of the body.$
Q.263 marks $(a) Explain how it is ensured that the orchid Ophrys is pollinated by a specific species of bee. (b) Describe co-evolution with the help of this example.$
Q.273 marks $Explain the mode of action of contraceptive pills taken by human females. Mention the schedule to be followed for effective outcome.$
Q.28 (a)3 marks $(i) What are transgenic animals ? (ii) Name the first transgenic cow and state its importance.$
OR
Q.28 (b)3 marks $(i) Explain the convention for naming EcoRI. (ii) With the help of an illustration only, show the action of EcoRI on a DNA Polynucleotide.$

Section D

Isn't it incredible that India's land area is only $2{\cdot}4$ per cent of the world's total land area whereas its share of the global species diversity is an impressive $8{\cdot}1$ per cent ! However, in these estimates of species, prokaryotes do not figure anywhere. Biologists are always keen on collecting data with respect to species diversity observed in different regions of the world. The data collected based on the survey conducted for species richness of groups of mammals in three different regions of the world is shown in the bar graph given below :
Q.29 (a)1 mark $Why is the species richness maximum in Region III in the bar graph ?$
OR
Q.29 (a) OR1 mark $Why is the species richness minimum in Region I in the bar graph ?$
Q.29 (b)1 mark $Plants and animals do not have uniform diversity in the world but show rather uneven distribution. Mention what this kind of diversity is referred to as.$
Q.29 (c)2 marks $Why is it that prokaryotes do not have an estimated number of their species diversity as seen in plants and animals ? Explain.$
Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow :
Q.30 (a)1 mark $Identify the colony that has got transformed. Justify your answer.$
Q.30 (b)2 marks $What are the sites in a plasmid called where ampicillin and tetracycline resistance genes are inserted ? State their role in genetic engineering.$
Q.30 (c)1 mark $Name two enzymes playing an important role in genetic engineering.$
OR
Q.30 (c) OR1 mark $\beta$

Section E

5 marks each

Q.31 (a)5 marks $(i) Draw a labelled diagram of the embryonic stage that gets implanted in the human female leading to pregnancy. (ii) Explain the changes that the different parts of the embryo undergo after implantation up till (1) Placenta formation and (2) formation of three germ layers. (iii) Mention the role of the following : (1) Placenta (2) Three germ layers$
OR
Q.31 (b)5 marks $(i) Why do plants like Viola and Oxalis give assured seed sets even in the absence of pollinators ? When an orange seed is squeezed, many embryos of different shapes and sizes are observed. Why ? (ii) Mention four advantages of seed formation to angiosperms. (iii) Draw a diagram of a fertilized embryo sac of an angiosperm and label any four parts.$
Q.32 (a)5 marks $(i) Name and explain the property present in normal cells but is lost in cancer cells. (ii) All normal human cells have genes that may become cancerous under certain conditions. Name them and explain how. (iii) State the role of the following techniques in detection and diagnosis of cancer : (1) Biopsy and Histopathology (2) Magnetic Resonance Imaging$
OR
Q.32 (b)5 marks $\downarrow$
Q.33 (a)5 marks $Stability, as one of the properties of genetic material, was very evident in one of the very early experiments in genetics. Name the scientist and describe his experiment. State the conclusion he arrived at.$
OR
Q.33 (b)5 marks $A tall pea plant bearing violet flowers with unknown genotype is given. Find the genotype by working out different crosses only by selfing the plants. Write the genotypic and phenotypic ratios of each cross shown by you.$