By QB365 on 31 Dec, 2022
QB365 provides a detailed and simple solution for every Possible Questions in Class 12 Biology Subject - Revision Model Question Paper, English Medium. It will help Students to get more practice questions, Students can Practice these question papers in addition to score best marks.
12th Standard
Biology
PART-I
Note : i
) All Questions Are Compulsory
ii) Choose The Most Suitable Answer From The Given
Four Correct Alternatives
The mode of sexual reproduction in bacteria is by ______.
Formation of gametes
Endospore formation
Conjugation
Zoospore formation
The foetal membrane that forms the basis of the umbilical cord is _____.
Allantois
Amnion
Chorion
Yolk sac
Which of the following statements about DNA replication is not correct?
Unwinding of DNA molecule occurs as hydrogen bonds break.
Replication occurs as each base is paired with another exactly like it
Process is known as semi conservative replication because one old strand is conserved in the new molecule.
Complementary base pairs are held together with hydrogen bonds
B cells that produce and release large amounts of antibody are called
Memory cells
Basophils
Plasma cells
killer cells
Cyclosporin – A is an immunosuppressive drug produced from _______
Aspergillus niger
Manascus purpureus
Penicillium notatum
Trichoderma polysporum
Which of the following is an r-species
Human
Insects
Rhinoceros
Whale
Right to Clean Water is a fundamental right, under the Indian Constitution
Article 12
Article 21
Article 31
Article 41
Match the following
I) | External fertilization | i) | pollen grain |
II) | Androecium | ii) | anther wall |
III) | Male gametophyte | iii) | algae |
IV) | Primary parietal layer | iv) | stamens |
I | II | III | IV |
iv | i | ii | iii |
I | II | III | IV |
iii | iv | i | ii |
I | II | III | IV |
iii | iv | ii | i |
I | II | III | IV |
iii | i | iv | ii |
In pea plants, yellow seeds are dominant to green. If a heterozygous yellow seed plant is crossed with a green seeded plant, what ratio of yellow and green seeded plants would you expect in F1 generation?
9:1
1:3
3:1
50:50
Restriction enzymes are _____.
Not always required in genetic engineering
Essential tools in genetic engineering
Nucleases that cleave DNA at specific sites
both b and c
Ecology is the study of an individual species is called
i) Community ecology
ii) Autecology
iii) Species ecology
iv) Synecology
i only
ii only
i and iv only
ii and iii only
Which of the following ecosystem has the highest primary productivity?
Pond ecosystem
Lake ecosystem
Grassland ecosystem
Forest ecosystem
The plants which are grown in silivpasture system are ______.
Sesbania and Acacia
Solenum and Crotalaria
Clitoria and Begonia
Teak and sandal
Colostrum provides
Naturally acquired active immunity
Naturally acquired passive immunity
Artificially acquired active immunity
Artificially acquired passive immunity
______ is not a feature of acquired immunity.
diversity
recognitionof self
non-specific
memory
PART-II
Note : i ) Answer any six questions and question number 24 in compulsory.
At what stage of development are the gametes formed in new born male and female?
Name the parts marked ‘A’ and ‘B’ in the given transcription unit:
PCR is a useful tool for early diagnosis of an Infectious disease. Elaborate
What is reproduction?
What is the difference between missense and nonsense mutation?
What is the name of the process given below? Write its 4 types.
Give correct answers for the given questions below.
a. Identify the vegetative propagules
b: Label the part
c. Can offspring produced be considered as clone?
d. Write as the binomial of the above.
Who rediscovered Mendel's results on the inheritance of characters?
Given below are the secondary metabolites. Mention their plant source.
(a) Digoxin
(b) Vincristine.
PART-III
Note : i ) Answer any six questions and question number 24 in compulsory.
The unicellular organisms which reproduce by binary fission are considered immortal. Justify
Identify the given image and label its parts marked as a, b, c and d
Select the correct term from the bracket and complete the given branching tree
(Barriers, Lactational amenorrhoea, CuT, Tubectomy)
Differentiate between Tundra and Taiga Biomes.
Write the advantages and disadvantages of Bt cotton.
Differentiate between:
Autoimmune disease and Immunodeficiency disease
(i) Identify the Process
(ii) Name the Organism
Give the alternate terminologies for
(a) Spermatogonia
(b) Embryonic ectoderm
Complete the table by filling the gaps.
Disease | Causative agent | Symptoms |
Gonnorrhea | A | Affects urethra & cervix, painful urination |
B | Human Immuno Virus | Enlarged lymph node, night sweat, weight reduction |
Hepatitis | Hepatitis-B- Virus | C |
PART-IV
Note : i
) Write all the following questions.
The following is the illustration of the sequence of ovarian events (a-i) in a human female.
a) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents.
b) Name the ovarian hormone and the pituitary hormone that have caused the above-mentioned events.
c) Explain the changes that occurs in the uterus simultaneously in anticipation.
d) Write the difference between C and H.
a) Identify the figure given below
b) Redraw the structure as a replicating fork and label the parts
c) Write the source of energy for this replication and name the enzyme involved in this process.
d) Mention the differences in the synthesis of protein, based on the polarity of the two template strands.
Explain how “Rosie” is different from a normal cow
Describe dominant epistasis with an example.
Write the protocol for artificial seed preparation.
Write the economic importance of rice.
Write a note a extra embryonic membranes.
List out the causes of fertility in human.
Discuss the genic balance mechanism of sex determination with reference to Drosophila.
Write the salient features of Human Genome Project.
Answers
Conjugation
Allantois
Replication occurs as each base is paired with another exactly like it
Plasma cells
Trichoderma polysporum
Insects
Article 21
I | II | III | IV |
iii | iv | i | ii |
50:50
both b and c
ii and iii only
Forest ecosystem
Sesbania and Acacia
Naturally acquired passive immunity
non-specific
Development of female gamete is called oogenesis. Oogenesis starts at the beginning of puberty.
Development of male gamete is called spermatogenesis. Spermatogenesis starts at puberty
A - \(5^{\prime} \rightarrow 3^{\prime}\) is called a coding strand.
B - \(3^{\prime} \rightarrow 5^{\prime}\) is called a template strand.
(i) PCR is a very sensitive technique which enables the amplification of desired DNA from a limited amount of DNA template.
(ii) A technique can be also used for amplifications of RNA in which case it is referred to as reverse transcription PCR (RT-PCR). In this process the RNA molecules (mRNA) must be converted to complementary DNA by the enzyme reverse transcriptase (reverse transcription).
(iii) The cDNA then serves as the template for PCR.
(iv) The specificity and sensitivity of PCR is useful for the diagnosis of inherited disorders (genetic, viral; bacterial, diseases).
(v) Hence, it can detect the presence of an infectious organism in the infected patient at an early stage of infection (even before the infectious organism has multiplied into large number).
Reproduction is a biological process in which an organism give rise to offsprings. This helps to maintain continunity of its species.
Missense Mutation | Non-sense Mutation |
The mutation where the codon for one amino acid is changed into a codon for another amino acid. |
The mutations where codon for one amino acid is changed into a termination or stop codon. |
Name of the process-Plant tissue culture Types:
(a) Organ culture
(b) Meristem culture
(c) Protoplast culture
(d) Cell culture
a - Tuber
b - Bud from eye
c - Yes
d - Solanum tuberosum.
Three scientists (de Vries, Correns and Tschermak) independently rediscovered Mendel's results on the inheritance of characters.
(a) Digoxin is obtained from Digitalis purpuria.
(b) Vincristine is obtained from Catharanthus roseus.
1. In unicellular organism there is no special structure for reproduction.
2. In binary fission the entire parent body constitute the reproductive unit and disappears when its division into two daughter unicellular cell is completed.
3. These two daughter cells function as two new individuals.
4. There is no remains of parent body cell and parent cannot be said to have died.
5. In fact after binary fission parent continues living as two daughter individual.
Hence, the unicellular organisms which undergo binary fission are called immortal (no natural death).
Human Ovum
a - Vitelline membrane
b - Nucleus
c - Zona Pellucida
d - Corona radiata
A - Barrier methods
B - Lactational amenorrhoea
C - Tubectomz
D - CuT
No. | Tundra Biome | Taiga Biomes |
---|---|---|
1. | This is almost treeless plain in the northern parts of Asia, Europe, and North America. | Taiga is a forest of coniferous trees such as spruce, fir and pine. |
2. | Winters are long with little daylight, summers are short, with long daylight hours. | Summer temperature ranges from 10octo 21oPc. |
3. | Because of the severe winters, many of the animals are migratory. For E g: the many shore birds and water fowl such as ducks and geese, nest in the Tundra during the summer and migrate south for the winter. |
lmportant migratory herbivores include moose, elk, deer and reindeer. Moose and reindeer migrate to the Taiga for winter and to Tundra for summers. |
The advantages of Bt cotton are:
1. Yield of cotton is increased due to effective control of bollworms.
2. Reduction in insecticide use in the cultivation of Bt cotton
3. Potential reduction in the cost of cultivation.
Disadvantages
Bt cotton has some limitations:
1. Cost of Bt cotton seed is high.
2. Effectiveness up to 120 days after that efficiency is reduced.
3. Ineffective against sucking pests like jassids, aphids and whitefly.
4. Affects pollinating insects and thus yield.
S.No | Autoimmune disease | Immunodeficiency disease |
i. | If the immune system of the body fails to distinguish foreign molecules from self, then it reacts destructively against the host's own molecules. This is known as autoimmune disease. |
An immunodeficiency disease results from the failure of one or more components of the immune system which could be due to genetic reasons, radiation, infections etc., |
ii. | Eg: Multiple sclerosis is a autoimmune disease | Eg: AIDS is a Immunodeficiency disease. |
(i) Longitudinal binary fission
(ii) Euglena
(a) Spermatogonia = Sperm mother cell
(b) Embryonic ectoderm = hypoblast
A - Neisseria Gonorrhoea
B - AIDS
C - Jaundice
(a) The figure 'F' represent ovulation.
Stage of oogenesis - Ovulatory or luteal stage of oogenesis
(b) (i) The ovarian hormone is progesterone which is released during ovulation.
(ii) The pituitary hormones are the follicle-stimulating hormone (FSH) and Luteinizing hormone (LSH) which are released during and ovulation from anterior pituitary gland.
(c) The endometrium of the uterus gets thickened and blood supply to the endometrium increase.
(d) Figure 'C' represents the secondary follicle and figure h represents the degenerating corpus luteum.
Secondary follicle | Corpus luteurn |
lt is surrounded by layers of granulosa cells | Absence of granulosa cells |
Theca layer is present | Theca layer is absent. |
(a) Replicating fork of DNA
(b)
(c) Source of Energy:
NTP's are used in the synthesis of RNA primers and ATP is used as an energy source for some of the enzymes, needed to initiate and sustain DNA synthesis occurs at the replication fork.
Enzymes involved in replication :
(i) DNA Helicase
(ii) DNA polymerase
(iii) Topoisomerase/DNA Gyrase
(iv) DNA ligase
(v) Primase
(d) Both the strands of (parental) DNA act as template for the synthesis of new strands
1. On the templates strand with \(3^{\prime} \rightarrow 5^{\prime}\) polarity the new strand (leading strand) is synthesized as a continuous stretch. It is called continuous synthesis (DNA polymerase carryout polymerisation).
2. On the other strand \(5^{\prime} \rightarrow 3^{\prime}\) polarity DNA synthesized as short stretches; it is called discontinuous synthesis.
3. Later the short stretches of DNA are joined by DNA-ligases into a continuous strand called lagging strand.
1. In 1997, Rosie, the first transgenic cow produced human protein enriched milk, which contained the human alpha lactalbumin.
2. Alpha lactalbumin is a protein composed of 123 amino acidi and 4 disulphide bridges, with a molecular weight of 14178 Da.
3. In human milk, & lactalbumin is the most abundant protein comprising 25% of total protein found in human milk.
4. It is synthesized by the mammary glands & lactalbumin binds calcium and zinc ions and possesses bactericidal antitumor activities.
Interlocus interactions take place between the alleles at different loci i.e between alleles of different genes
Dominant Epistasis: It is a gene interaction in which 2 alleles of a gene at one locus interfere & suppress or mask the phenotypic expression or mask the phenotypic expression of a different pair of alleles of another gene at another locus.
The gene that suppresses or masks the phenotypic expression of a gene at another locus is known as epistatic.The gene whose expression is interfered by non-allelic genes & prevents from exhibiting its character is known as hypostatic.
When both the genes are present together, the phenotype is determined by the epistatic gene and not by the hypostatic gene.
In the summer squash, the fruit colour locus has a dominant allele 'W' for white colour & a recessive allele 'w' for coloured fruit.
'W' allele is donminant that masks the expression of any colour. In another locus hypostatic allele 'G' is for yellow fruit and its recessive allele 'g' for green fruit.
In the first locus the white is dominant to colour where as in the second locus yellow is dominant to green.
When the white fruit with genotype WWgg is crossed with yellow fruit with genotype wwGG, the F1 plants have white fruit and are heterozygous (WwGg).
When F1 heterozygous plants are crossed they give rise to F2 with the phenotypic ratio of 12 white:3 yellow: 1 green.
Since W is epistatic to the alleles 'G' and 'g'. the white which is dominant, masks the eftect of yellow or green.
Homozygous recessive ww genotypes only can give the coloured fruits (4/16).
Double recessive 'wwgg' will give green fruit (1/16).
The Plants having only 'G' in its genotype (wwGg or wwGG) will give the yellow fruit(3/16).
Artificial Seed
1. Artificial seeds or synthetic seeds (synseeds) are produced by using embryoids (somatic embryos) obtained through in vitro culture.
2. They may even be derived from single cells from any part of the plant that later divide to form cell mass containing dense cyptoplasm, large nucleus, starch grains, proteins, and oils etc.
3. To prepare the artificial seeds different inert materials are used for coating the somatic embryoids like agrose and sodium alginate.
Common Name | Botanical name | Origin and area | Uses |
PADDY/ RICE:Semi aquatic crop grown in standing water. Second position next to wheat |
Oryza sativa | South East Asia - China, lndia, Thailand- Delta of TamilNadu |
1. Staple food with calcium in many southern hill regions of lndia. 2. Made in to Porridge and gruel. 3. Ragi malt - nutrient drink and fermented beverages |
The extra embryonic membranes namely the amnion, yolk sac allantois and chorion protect the embryo from dessication, mechanical shock and help in the absorption of nutrients and exchange of gases.
Amnion
The amnion is a double layered translucent membrane filled with the amniotic fluid. It provides a buoyant environment to protect the developing embryo from injury, regulates the temperature of the foetus and provides a medium in which the foetus can move.
Yolk sac:
The yolk sac forms a part of the gut and is the source of the earliest blood cells and blood vessels.
Allantois:
The allantois is an extra embryonic membrane which forms a small out pocketing of embryonic tissue at the caudal end of the yolk sac. It is the structural base for the umbilical cord that links the embryo to the placenta and ultimately it becomes part of the urinary bladder.
Chorion:
The chorion is the outermost membrane which encloses the embryo and all other membranes and also helps in the formation of the placenta.
Chorionic Villi:
The trophoblast cells in the blastocyst send out several finger like projections called chorionic villi carrying foetal blood and are surrounded by sinuses that contain maternal blood. The chorionic villi and the uterine tissues form the disc-shaped placenta.
Placenta:
Placenta is a temporary endocrine organ formed during pregnancy and it connects the foetus to the uterine wall through the umbilical cord. It is the organ by which the nutritive, respiratory and excretory functions are fulfilled.
Causes for male infertility:
(i) Undescended tests and swollen veins in scrotum
(ii) Underdeveloped testes
(iii) Tight clothing increases the temperature in scrotum and affect sperm production.
(iv) Autoimmune response against own sperm.
(v) Usage of alcohol, tobacco, marijuana drugs etc.
Causes for female infertility:
(i) Malformation of cervix or fallopian tubes.
(ii) Inadequate nutrition at puberty.
(iii) Low body fat (anorexia = psychological eating disorder due to fear of gaining weight) .
(iv) Pelvic Inflammatory Disease (PID), uterine disorders, endometriosis.
(v) underdeveloped ovaries.
(vi) Developing antibodies against sperm.
Common Causes for both the sexes:
(i) Tumours in pituitary or sex organs
(ii) Inherited mutation of hormone synthesizing genes
(iii) Long term stress
(iv) Ingestion oftoxins (Cadmium) & drugs
(v) Injuries to gonads
(vi) Ageing
(i) Genic balance mechanisms of sex determination in Drosophila was first studied by C. B. Bridges.
(ii) In Drosophila, the presence of Y chromosome is essential for the fertility of male sex, but does not determine the male sex.
(iii) The gene for femaleness is located on the X chromosome and those for maleness are located on the autosomes.
(iv) When geneticist C. B. Bridges, working with Drosophila, crossed a triploid (3n) female with a normal male, he observed many combinations of autosomes and sex chromosomes in the offspring.
(v) He suggested that sex In Drosophila is determined by the balance between the genes for femaleness located on the 'X' chromosomes and those for maleness located on the 'autosomes". Hence the sex of an individual is determined by the ratio of its X chromosome to that of its autosome sets. This ratio is termed sex index and is expressed as:
\(Sex \ index=\frac { Number \ of \ X \ Chromosomes }{ Number \ of \ Y \ Chromosomes } \left( \cfrac { X }{ A } \right) \)
(vi) Change in this ratio leads to a changed sex phenotype. The results obtained from a cross between triploid female Drosophila (3A:3X) with a diploid male (2A: XY) is shown in below.
(vii) Bridges classical cross of a triploid (3A+XXX) female fly and a diploid (2A+XY) male fly ♀ ♂
Triploid ♀ Diploid ♂
Parent 3A + XXX 2A + XY
Gametes (2A + XX) (A + X) (A + X) (A + Y)
(2A +X) (A+XX)
A + X | A + Y | |
---|---|---|
2A + XX | 3A + XXX Triploid Femle |
3A + XXY Triploid Intersex |
2A + X | 3A + XX Triploid Intersex |
3A + XY Super Male |
A + XX | 2A + XXX Super female |
2A+ XXY Diploid Female |
A + X | 2A + XX Diploid Female |
2A + XY Diploid Male |
Different doses of X chromosomes and autosome sets and their effect in sex determination in Drosphild
Phenotype | Number of 'X' Chromosomes (X) |
Number of Autosome sets (A) |
\(Sex \ Index=\frac { Number \ of \ X \ Chromosomes }{ Number \ of \ autosome \ sets } \) | |
---|---|---|---|---|
Metafemale/ Super female | 3 | 2 | 3/2 = 1.5 | |
Normal Female | Teraploid | 4 | 4 | 4/4 = 1.0 |
Triploid | 3 | 3 | 3/3 = 1.0 | |
Diploid | 2 | 2 | 2/2 = 1.0 | |
Haploid | 1 | 1 | 1/1 = 1.0 | |
Inter sex | 2 | 3 | 2/3 = 0.67 | |
Normal male | 1 | 2 | 1/2 = 0.50 | |
Meta male / super male | 1 | 3 | 1/3 = 0.53 |
A sex-switch gene in Drosophila directs female development. This gene, Sex-lethal (SxL) located on the X chromosome, has two states of activity. When it is 'on' it directs female development and when it is 'off' maleness ensures. Other genes located on the X chromosome and autosomes regulate this sex-switch gene. However, the Y- chromosome of Drosophila is required for male fertility.
i) Although human genome contains 3 billion nucleotide bases, the DNA sequences that encode proteins make up only about 5% of the genome.
ii) An average gene consists of 3000 bases, the largest known human gene being dystrophin with 2.4 million bases.
iii) The function of 50% of the genome is derived from transposable elements such as LINE and ALU sequence.
iv) Genes are distributed over 24 chromosomes. Chromosome 19 has the highest gene density. Chromosome 13 and Y chromosome have lowest gene densities.
v) The chromosomal organization of human genes shows diversity.
vi) There may be 35000-40000 genes in the genome and almost 99.9 nucleotide bases are exactly the same in all people.
vii) Functions for over 50 percent of the discovered genes are unknown.
viii) Less than 2 percent of the genome codes for proteins.
ix) Repeated sequences make up very large portion of the human genome. Repetitive sequences have no direct coding functions but they shed light on chromosome structure, dynamics and evolution (genetic diversity).
x) Chromosome 1 has 2968 genes, whereas chromosome 'Y' has 231 genes.
xi) Scientists have identified about 1.4 million locations, where single base DNA differences (SNPs - Single nucleotidepolymorphism - pronounce as 'snips') occur in humans. Identification of 'SNIPS' is helpful in finding chromosomal locations for disease associated sequences and tracing human history.