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FRAGMENT 2 EXAMINATION(2019-20)
SUBJECT :BIOLOGY(044)
CLASS:XII
TIME:3 HRS M.M:70
GENERAL INSTRUCTIONS:
There are a total of 27 questions and 4 sections in the question paper.All questions are
compulsory.
Section A contains question number 1 to 5,Very short answer type questions of 1 mark
each.
Section B contains question number 6 to 12, Short answer type I questions of 2 marks
each.
Section C contains question number 13 to 24, Short answer type II questions of 3
marks each.
Section D contains question number 25 to 27, Long answer type questions of 5 marks
each.
There is no overall choice in the question paper, however, an internal choice is
provided in 2 questions of 1 mark, 2 questions of two marks, 4 questions of three
marks and all 3 questions of five marks .In these questions, an examinee is to attempt
any one of the two given alternatives.
Wherever necessary, the diagram drawn should be neat and properly labelled.
SECTION-A
Q1 Coelocanth that was caught in 1938 in South Africa,was very
significant in the evolutionay history of vertebrates.Why?
(NCERT Pg-138)
1
Ans Coelocanth thought to be extinct.These animals were
lobefins,fish like,lived in both water and land,amphibians have
evolved from fish like organisms.
1
Q2 What did Louis Pasteur‟s experiment on killed yeast
demonstrate?Name the theory that got disproved on the basis of
his experiment. (NCERT Pg-127)
1
Ans Life comes from pre-existing life, theory of spontaneous
generation
½+½
or
Write the probable differences in eating habits of Homo habilis
and Homo erectus. (NCERT Pg-140)
Ans Homo habilis-did not eat meat, vegetarian ½
Homo erectus-ate meat, meat eater ½
Q3 A diploid organismis heterozygous for 4 loci, how many types
of gametes can be produced? (NCERT Pg-94.Q3)
1
Ans 2n,where n=no. of loci
n=4
2n=2
4=2 x 2 x 2 x 2=16
Q4 How many base pairs would a DNA segment of length1.36mm
have?
(NCERT Pg-99)
1
Ans Distance between 2 base pairs=0.34nm or 0.34x10-6
Number of base pairs in 1.36nm DNA segment =
x 1.36
=4x106 bp
or
Mention the carbon positions to which the nitrogenous base and
the phosphate molecule are respectively linked in the nucleotide
given below: (NCERT Pg-96)
Ans Nitrogenous base is linked to first carbon, Phosphate is linked to
fifth carbon
½ + ½
Q5 Why is the enzyme cellulose needed for isolating genetic
material from plant cells and not from the animal cells?
(NCERT Pg-201)
1
Ans Cellulase breaks down cellulose which is present in cell walls of
plants but absent in animal cells.
1
SECTION-B
Q6 Convergent evolution and divergent evolution are the two
concepts explaining organic evolution. Explain each one with
the help of an example. (NCERT Pg-130,131)
2
Ans Convergent evolution- Not anatomically similar structures
though they perform similar functions (different structures
evolving for the same function and hence having similarity )Eg-
Wings of butterfly and birds.
Divergent evolution- same structure developed along different
directions due to adaptations to different needs. Eg-forelimbs of
whales,bats,cheetah and human perform different functions but
have similar anatomical structure (or any other example)
1+1
or
How do Darwin’s finches illustrate adaptive radiation?
(NCERT Pg- 133)
Ans Original stock of seed eating finches migrated to different
habitats (of Galapagos Islands),adapted to different
feeding methods, by altered beak structure, evolved
into different types of finches.
1+1
Q7 Diagrammatically represent the experimental set up that proves
Oparin-Haldane hypothesis.(NCERT Pg-128)
2
Ans Pg-128 Diagram
Q8 a.
b.
Why is human ABO blood group gene considered a good
example of multiple alleles?
Work out a cross upto F1 generation only, between a mother
with blood group A and the father with blood group B. Explain
the pattern of inheritance exhibited.(NCERT Pg-77,78)
2
Ans a. More than two alleles govern the human ABO blood group gene ½
b
1
Codominance.When the two alleles IAI
A are present
together,both the alleles express each other equally
½
Q9 a.
(A) -- DNA mRNA Protein
1 ½
Look at the above sequence and mention the events (A),(B) and
(C).
b. What does Central Dogma state in Molecular Biology?
(NCERT Pg-98)
½
Ans a A-DNA replication,B-Transcription,C-Translation 1 ½
B DNARNAProtein ½
Q10 Why is DNA considered a better hereditary material than
RNA?(NCERT Pg-103)
2
Ans Chemically ess reactive (2‟OH group is absent therefore less
reactive than RNA)
1
Structurally more stable (presence of Thymine gives additional
stability to DNA)
1
Provides scope for slow changes (mutation) (Any two)
Q11 Write any four ways used to introduce a desired DNA segment
into a bacterial cell in recombinant DNA technology
experiments.(NCERT Pg-200)
Ans a. Microinjection ½
b. Biolistic/gene gun ½
c. Using disarmed pathogen vector ½
d. Divalent cations/Heat shock ½
Q12 Name the first transgenic cow.Which gene was introduced in
this cow?(NCERT EXEMPLAR Q13 Pg-85)
2
Ans Rosie, Human α-lactalbumin 1+1
OR
What are Cry proteins? Name an organism that produce it. How
B C
has man exploited this protein to his benefit?(NCERT Pg-
216,Q4)
Ans Crystal proteins, poisonous to some insects ½
Bacillus thuringiensis ½
Cry protein producing gene transferred to the plants to provide
resistance against insect larvae
½
Transgenic crops are produced eg-Bt cotton, Bt corn (Any other
eg)
½
SECTION-C
Q13 a.
b.
How does Hardy weinberg equation explain genetic
equilibrium.
Describe how does the equilibrium get disturb which leads to
founder effect. (NCERT Pg-137)
3
Ans a. p2+2pq+q
2=1,sum total of all the allelic frequencies is 1
b. Genetic drift i.e.changes in allele frequencies of population
occurring by chance.
1
Change in allele frequency may be so different that the
population becomes a different species,the original population
becomes founder
1
Q14 Differentiate between the explanations given by Darwin and de
vries respectively on the mechanism of evolution.(3points )
(NCERT Pg-135)
OR
Rearrange Ramapithecus,Australopithecus and Homo habilis in
the order of their evolution on the earth.Comment on their
evolutionary characteristics. (NCERT Pg-141)
3
Ans Darwin-Evolution was gradual(stepwise) ½
Variations and natural selection occurs through a number of
generations and responsible for speciation
½
Darwin‟s variations are small and directional ½
De vries- Evolution occurred in a single step(saltation) ½
Single step mutation caused speciation ½
Mutations are random and directionless ½
OR
RamapithecusAustralopithecusHomo habilis 1½
Ramapithecus-were hairy and walked like gorilla and
chimpanzees.They were more man like
½
Australopithecus-hunted with stone weapons and ate fruit ½
Homo habilis-Brain capacity 650-800,probably did not eat meat ½
Q15 a. Explain the mechanism of sex determination in
humans.(NCERT Pg-87)
3
b. Differentiate between male heterogamety and female
heterogamety with the help of example of each.(NCERT Pg-86)
Or
Give an example of an autosomal recessive trait in
humans.Explain its pattern of inheritance with the help of a
cross.(NCERT Pg-90)
Ans a.
1
b. Male heterogamety-(XY type, XO type) ½
Male produces two types of gametes
Human beings, grasshopper ½
Female heterogamety-(ZW type) ½
Female produces two types of gametes
Birds, fowl, fishes ½
or
Sickle cell anaemia (or any other) ½
Disease controlled by single pair of alleles HbA and Hb
S ½
HbSHb
S-show the diseased homozygous phenotype ½
HbAHb
S-Heterozygous,carrier ½
HbAHb
A-Normal
*
1
Q16 What is point mutation? Expain with the help of one
example(NCERT Pg-94 Q14)
3
Ans Gene mutation that arise due to change in a single base pair of
DNA.
1
Sickle cell anaemia, GAGGUG, A replaced by U 1
Sixth codon of the b globin chain of hb molecule that causes ½+½
substitution of Glutamic acid by Valine
Q17. Describe how the lac operon operates,both in the presence and
absence of inducer in E.Coli.(NCERT Pg-116,117)
3
Ans NCERT Pg.117,fig.6.4 1½ +
1½
Q18. a. Draw a labeled diagram of a “replicating fork”showing the
polarity.Why does DNA replication occur within such „forks‟?
3
b. Name two enzymes involved in the process of DNA
replication,along with their properties.(NCERT Pg-107)
Ans a. NCERT Pg.107, Fig. 6.8 ½
Two strands of DNA cannot be separated in its entire length due
to very high energy requirements.
½
b. i) DNA dependent DNA polymerase: Polymerisation of
deoxynucleotides only in 5′ to 3′ direction
1
ii) DNA ligase: joins the discontinuously synthesized DNA
fragments during replication.
1
OR
DNA sequences that
contain small segments
which are repeated
many times.
Satellite DNA are types of
repetitive DNA sequences
that contain highly repetitive
DNA
mRNA acts as a
template for the process
of transcription
Acts as an adapter molecule
that carries a specific amino
acid to mRNA for synthesis
of polypeptide.
Acts as a template for
the synthesis of mRNA
Complementary strand of
template strand
Q19. a. What do „Y‟and „B‟stand for in „YAC‟ and “BAC‟used in
HGP.Mention their role in the project.
3
b. Write the percentage of total human genome that codes for
proteins and the percentage of discovered genes whose
functions are known as observed during HGP.
c. Expand „SNP‟s identified by scientists in HGP.(NCERT Pg-
119,120)
Ans a. Yeast, Bacterial ½+½
Used as vectors for cloning foreign DNA ½
b. (<)2%, (<)50% ½+½
c. Single Nucleotide Polymorphism ½
Q20. a. Name the selectable markers in the cloning vector pBR322?
Mention the role they play.
3
b. Why is the coding sequence of an enzyme β-galactosidase is a
preferred selectable marker in comparison to the ones named
above?(NCERT Pg-199)`
Ans a. ampR, tet
R help in identifying and eliminating
nontransformants/nonrecombinants and selectively permitting
the growth of the transformants/recombinants
½+½
+½
b. Simpler and less cumbersome. ½
In the presence of chromogenic substrate recombinants form
colourless colonies and non recombinants form blue coloured
colonies.
½+½
Q21 A. Study the diagram given below and answer the questions that
follow(NCERT Pg-198)
3
a. Why have DNA fragments in band „D‟moved farther away in
comparison to those in band „C‟?
b. Identify the anode end in the diagram.
c. How are these fragments visualised?
B. What modification is done in the Ti plasmid of Agrobacterium
tumefaciens to convert it into a cloning vector?(NCERT
EXEMPLAR Pg-79,Q10)
Ans a. DNA fragments in band „D‟ are smaller in size than fragments
in band „C‟.
½+½
b. „B‟ ½
c. Staining the DNA with ethidium bromide followed by exposure
to UV radiations.
½
B. Plasmid is disarmed by deleting the tumour inducing genes 1
Q22. List the three molecular diagnostic techniques that help detect
pathogens from suspected patients. Mention one advantage of
these techniques over conventional methods.(NCERT Pg-212)
3
Ans 1. Recombinant DNA technology ½
2. PCR ½
3. ELISA ½
Help in early diagnosis of the disease even when the bacteria or
virus concentration is very low and no symptoms are visible for
the disease.
1 ½
Q23. How did Eli Lilly synthesise the human insulin? Mention one
difference between this insulin and the one produced by the
human pancreas.(NCERT Pg-211)
OR
What is Biopiracy?State the initiative taken by the Indian
Parliament towards it.(NCERT Pg-214)
3
Ans Prepared two DNA sequences corresponding to A and B chains
of human insulin
½
Introduced them in plasmids of E.coli to produce insulin chains. ½
Chain A and B are combined by disulfide bonds to form human
insulin.
1
Difference-Synthesised insulin did not contain C-peptide and
was directly prepared in mature form.
1
OR
Use of bioresources by organizations without proper
authorization from the countries and people concerned without
compensatory payment.
1 ½
Govt. has cleared the second amendment of the Indian patent
bills, emergency provisions and Research and development
initiative.
½ + ½
+ ½
Q24 a.
b.
Name the deficiency for which first clinical gene therapy was
given.
Mention the causes of and one cure for this cure for this
deficiency.
(NCERT Pg-211)
3
Ans a. Adenosine deaminase deficiency(ADA) 1
b. Cause-Deletion of ADA gene 1
Cure- Bonemarrow transplantation/Enzyme replacement 1
therapy/giving functional ADA to patient by
injection/infusionof genetically engineered lymphocytes
/introducing gene isolated from marrow cells producing ADA
into cells at early embryonic stage. (any one)
SECTION-D
Q25. a.
b.
a.
b.
c.
State and explain the law of segregation as proposed by Mendel
in a monohybrid cross.
Write the mendelian F2 phenotypic ratio in a dihybrid cross.
State the law that he proposed on the basis of this ratio.How is
this law different from the law of segregation?(NCERT Pg-75)
OR
How does a chromosomal disorder differ from a Mendelian
disorder.
Name any two chromosomal aberration associated disorders.
List the characteristics of the disorders mentioned above that
help in their diagnosis.(NCERT Pg-91)
5
Ans a. Law states that the factors or alleles of a pair segregate from
each other during gamete formation such that a gamete receives
only one of the two factors.They do not show any blending.
1
NCERT Pg.79,Fig 5.7 1 ½
b. 9:3:3:1, Law of Independent Assortment 1 + ½
According to this law the two factors of each character assort or
separate out independent of the factor of other characters at the
time of gamete formation and get randomly rearranged in the
offspring producing both parental and new combinations of
characters.
1
OR
Mendelian disorder- Mainly due to alteration or mutation in
the single gene
1
Follows Mendel‟s principles of inheritance
May be recessive or dominant in nature
Eg. Haemophilia,Sickle cell anaemia
or
Chromosomal disorder-Due to absence or excess of abnormal
arrangement of one or more chromosome
Doesnot follow Mendel‟s principles of inheritance
Always dominant in nature
Eg. Turner‟s syndrome (or any other eg) (any two differences)
b. Down‟s syndrome, Klinefelter‟s syndrome (or any other eg) ½ ½
c. Down‟s syndrome- short statured with small round
head,furrowed tongue and partially opened mouth, palm is
broad with characteristic palm crease. Physical,psychomotor
and mental development is retarded (any three)
1 ½
Klinefelter‟s syndrome- Overall masculine development
,however the feminine development (development of breast i.e.
Gynaecomastia) sterile individuals.(three)
1 ½
Q26
a.
b.
c.
d.
e.
f.
Answer the following questions based on Meselson and Stahl's
experiment.(NCERT Pg-105)
Why did the scientist use 15
N H4Cl and 14
N H4Cl as source of
nitrogen in the culture medium for growing E.coli?
Name the molecules that 15
N got incorporated into.
How did they distinguish between 15
N labelled molecules from 14
N ones?
Mention the significance of taking the E.coli samples at definite
time intervals for observations.
Write the observations made by them from the samples taken at
the end of 20 minutes and 40 minutes respectively.
Write the conclusions drawn by them at the end of their
experiment.
OR
a. How did Griffith explain the transformation of R strain (non-
virulent) bacteria into a S strain (virulent)?
b. Explain how MacLeod, McCarty and Avery determined the
biochemical nature of the molecule responsible for transforming
R strain bacteria into S strain bacteria.
(NCERT Pg-100)
5
Ans a. 15
N is the heavy isotope of nitrogen and it can be separated from 14
N based on the difference in their densities.
1
b. 15
N was incorporated into newly synthesised DNA . ½
c. The two molecules were distinguished by caesium chloride
centrifugation in which these two separated into two different
bands at different positions based on their densities.
1
d. E.coli culture is taken at equal intervals to know the progress of
the experiment as generation time of E.coli is 20 minutes.
1
e. After 20 minutes the culture had an intermediate density and
after 40 minutes the culture had equal amount of hybrid DNA
and the light DNA
1
f. DNA replicates semiconservatively ½
OR
a.
*
S strain inject into mice Mice die 2
R strain inject into mice Mice live
S strain (heat killed) inject into mice Mice live
S srain( heat killed)+ R strain(live) inject into mice
Mice die`
b. They purifies biochemicals(Proteins, DNA, RNA) from heat
killed S type cells.
Proteases and RNases did not affect transformation so the
transforming substance was not a protein or RNA.
1
DNase inhibit transformation. 1
DNA is the genetic material 1
Q27 a. Name two commonly used bioreactors. State the importance of
using a bioreactor.
5
b. Draw a labeled sketch of most commonly used bioreactor and
describe its working.(NCERT Pg-204)
OR
a. List the three steps involved in PCR.
b. Name the source organism of Taq polymerase.Explain the
specific role of this enzyme in PCR.(NCERT Pg-202)
c. Mention one application of ELISA
Ans a. Simple Stirred tank, Sparged stirred tank
½ + ½
Importance- 1
1. Processing large volume of culture
2. Large scale production of recombinant proteins
3. Biologically converting raw materials into specific products
(any two)
b. NCERT Pg-204 3
OR
a. 1. Denaturation
2. Primer annealing
3. Extension of primers
1
1
1
b. Thermus aquaticus ½
Heat tolerant and can repeatedly amplify DNA at high
temperature.
½
c. Diagnosis test for AIDS 1
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