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