Download SAMPLE PAPER CLASS XII MM:70 TIME : 3 HRS General

SAMPLE PAPER
CLASS XII
MM:70
TIME : 3 HRS
General instructions
i) All questions are compulsory.
ii) The question paper consists of four sections A,B, C, D and E . Section-A contains 8 questions of
1 mark each. Section B is of 8 questions of 2 marks each. Section C is of 9 questions of 3 marks
each, and section E is of 3 questions of 5 marks. Section D is a value based question.
iii) Wherever necessary, the diagrams drawn should be neat and properly labeled
SECTION A
(1Mark)
1) What does ‘competent’ refer to in competent cells used in transformation
experiments?
2) Suggest any two techniques which can help in early detection of bacterial/viral
infections much before the symptom appear in the body?
3) Which is the site of control of gene expression in prokaryotes?
4) State the principle on which ELISA works?
5) What is the characteristic of pollen grain which undergoes water pollination
6) Write the scientific name of the plant where morphine is extracted
7) What is meant by competitive release in an ecosystem?
8) Banana is a fruit but also a parthenocarpic fruit. Give reason
SECTION B
( 2 Marks)
1)Draw the structure of an antibody and explain all its parts
2) Why do species with abiotic mode of pollination produce larger number of pollen
grains as compared to those with biotic mode?
3)How does RNA interference help in developing resistance in tobacco against
nematode infection?
4)Describe the two additional processes hnRNA has to undergo?
5)a) Expand IUDs
b) Why is a hormone releasing IUD considered as a good contraceptive to space
children.
6) How does test cross help in identifying the genotype of the organism?
7) List the parameters used for constructing ecological pyramids .Describe any one
instance where the pyramid may look inverted.
8)What is DNAfingerprinting .Mention its application?
SECTION C
(3 Marks)
1) What is the role of each of the following in body defence
i)Antihistamine
ii)Pyrogens
iii)Suppressor T cells
2) Construct an ideal pyramid of energy ,Where 1,000,000 joules of sunlight is
available.Label all its trophic level.
3) You have read that a single gene controls starch synthesis or size of the starch
grains and the seed shape in pea plant. The genotype Bb produces round seeds with
intermediate sized starch grain. Explain
4) How are assisted reproductive technologies helpful to humans? How are ZIFT and
GIFT different from intrauterine transfers? Explain
5) Explain the process of translation in a bacterium
6) i)Why is tRNA called an adaptor
ii) Draw and label a secondary structure of tRNA. How does the actual structure of
tRNA look alike
7) Draw the structure of a cloning vector .Label all its parts and mention their
function
8) In an angiosperm ,the embryo sac is haploid,zygote is diploid and endosperm is
triploid.justify giving reasons for each stage.
9) i)Mention the contribution of the following scientists:
a) Wilkins and Rosalind Franklin
b) Erwin Chargaff
ii)Draw a double stranded dinucleotide chain with all the four nitrogenous bases
SECTION D
(4 Marks)
1)Ravi is trying to convince his brother that in human chromosome many genes are
present. He took the example of chromosome no 1 which has 2968 genes. On an
average ,each gene consist of 3000 bases. Give the answer to his brother’s following
questions?
a)How such a long DNA molecule is packed within the chromosome.
b)What are codons and what are their property?
c)What are monocistronic and polycistronic genes?
d)What value do you learn from a eukaryotic DNA molecule?
SECTION E
(5 Marks)
1)If a desired gene is identified in an organism for some experiments ,explain the
process of the following:
i)Cutting the desired gene at a specific location.
ii)Synthesis of multiple copies of desired gene.
2) Explain the role of DNA –dependent RNA polymerase in initiation,elongation and
termination during transcription in bacterial cells
How is transcription more complex process in eukaryotic cells?Explain.
3)Study the schematic representation of the genes involved in the lac operon given
below and answer the following questions that follow:
p
i
P
o
z
y
a
i)Identify and name the regulatory genes in this operon. Explain its role in “switching
off” the operon
ii)Why is lac operon’s regulation referred to as negative regulation?
iii) Name the inducer molecule and the products of the genes ‘z’ and ‘y’ of the operon
.Write the function of these genes.