ISC Biotechnology 2012 Class-12 Previous Year Question Papers Solved

ISC Biotechnology 2012 Class-12 Previous Year Question Paper Solved for practice. Step by step Solutions with Questions of Part-1 and Part-2 (Section A , Section-B). By the practice of Biotechnology 2012 Class-12 Solved Previous Year Question Paper you can get the idea of solving.

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ISC Biotechnology 2012 Class-12 Previous Year Question Paper Solved

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Maximum Marks: 80
Time allowed: Three hours

  • Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
  • Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
  • The intended marks for questions or parts of questions are given in brackets [ ].
  • Transactions should be recorded in the answer book.
  • All calculations should be shown clearly.
  • All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part -1 (20 Marks)
(Answer all questions)

ISC Biotechnology 2012 Class-12 Previous Year Question Paper Solved 

Question 1.
(a) Mention any one significant difference between each of the following: [5] (i) Hybrid and Cybrid.
(ii) DNA polymerase and Taq DNA polymerase.
(iii) Glycosidic bond and Peptide bond,
(iv) Oils and Waxes.
(v) Homopolysaccharide and Heteropolysaccharide.

(b) Answer the following questions : [5]
(i) What is a callus?
(ii) Name the method used for the sterilization of plant hormones and vitamins.
(iii) Why is DNA replication called semi-conservative replication?
(iv) What is a promoter gene?
(v) State two uses of stem cells.

(c) Write the full form of the following :
(i) HGP
(ii) STS
(iii) CSIR
(iv) LAF
(v) SCP

(d) Explain briefly:
(i) Amphipathic property of lipids.
(ii) Replication fork
(iii) Androgenesis
(iv) Transamination.
(v) Active site.
Answer 1:

(i) Hybrid: Plants produced through the fusion of protoplasts of two different plant species/varieties is called hybrid.

Cybrid: Cybrid or cytoplasmic hybrid are cells or plant containing nucleus of one species but cytoplasm from both the parental species.

(ii) DNA polymerase: A DNA polymerase is an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand in DNA replication.

Taq DNA polymerase: Taq polymerase, is a thermostable DNA polymerase, originally isolated from bacterium Thermits aquaticus. It is used in polymerase chain reaction.

(iii) Glycosidic bond: A glycosidic bond (C-O-C) is a type of covalent bond that joins a aldose or ketone group of a carbohydrate (sugar) molecule to another group (OH) which may or may not be another carbohydrate.

Peptide bond: A peptide bond (HN – C = 0) is a chemical bond formed between two amino acids when the carboxyl group of one amino acid molecule reacts with the amino group of the other amino acid molecule. thereby releasing a molecule of water.

(iv) Oils: Oils are the esters of unsaturated fatty acid with glycerol. Oils are liquid at room temperature and have low melting point.

Waxes: Waxes are esters of fatty acid other than glycerol. They contain one molecule of long chain fatty acid esterified with one molecule of long chain like cytyl, ceryl or mericvl, mono hydroxy’ alcohol.

(v) Homopolysaccharide: Homopolysaccharides are the complex carbohydrates formed by polymerisation of the monosaccharide monomers.

Heteropolysaccharide: Heteropoly saccharides are the complex carbohy drates w hich are produced by the condensation of more than one type of monosaccharide monomers or their derivatives e.g., chitin, agar.


(i) Callus is a mass of meristematic, undifferentiated cells derived from plant tissue (explants).

(ii) The autoclaving denatures the vitamins and hormones, therefore, the solution of these compounds are sterilized by using Millipore filter paper with pore size of 0.2 micrometer diameter.

(iii) Semi-conservative is that mode of replication in which out of the two DNA strands, one is conserved strand and the other is newly synthesised.

(iv) A promoter gene is a segment of DNA containing the enzyme RNA polymerase that initiates the transcription of the genetic code.

(v) Uses of stem cells :
(1) Bone marrow transplants that are used to treat leukemia (blood cancer).
(2) Treatment for muscular dystrophy.

(c) (i) HGP: Human Genome Project.

(ii) STS: Sequence Tagged Sites.

(iii) CSIR : Council of Scientific and Industrial Research.

(iv) LAF: Laminar Air Flow.

(v) SCP: Single Cell Protein. .


 (i) Amphipathic nature : Most membrane lipids are amphipathic, having a non-polar end and a polar end. The amphiphilic nature of some lipids allows them to form structures such as vesicles, liposomes, or membranes in an aqueous environment.

(ii) The point at which the two strands of DNA are separated to allow replication of each strand is known as replication fork.

(iii) Androgenesis is the development of an embryo containing only paternal chromosomes due to failure of the egg to participate in fertilization.

(iv) Transamination is the process of transfer of the a-amino group from the amino acid to an a-keto acid.

(v) Active site is part of an enzyme where substrates bind and undergo a chemical reaction.

Part – II (50 Marks)
(Answer any Five questions)

ISC Biotechnology 2012 Class-12 Previous Year Question Paper Solved 


Question 2.
(a) Explain the general structure of an amino acid. What do you understand by essential and non-essential amino acids? [4] (b) What are cloning vectors ? Write the main characteristics of any three types of cloning vectors. [4] (c) What is a Codon ? Name the start codon and any one end codon. [2] Answer 2:
(a) Amino acids are building blocks of macromolecular proteins. They contain amino group and carboxyl group as functional groups.
On the basis of nutritional values amino acids are of two types :
Essential amino acids : These are essential for our body but they are not synthesised inside our body are termed as essential amino acids e.g., valine, leucine, isoleucine, lysine, phenylalanine, methionine, threonine, histidine, arginine.

Non-essential amino acids : They are those which are synthesised through transformation and transamination inside our body e.g., serine, alanine etc.
ISC Biotechnology Question Paper 2012 Solved for Class 12 1
(b) Cloning vector is a self-replicating DNA molecule that carries foreign DNA insert into a host cell, replicates inside a bacterial (or yeast) cell and amplify to produce many copies of itself and the foreign DNA.

Plasmid: It is an extra chromosomal circular DNA molecule that self replicates inside the bacterial cell and some yeast; cloning limit: 100 to 10,000 base pairs or 0.1-10 kilobases (kb).

Phage : Designed bacteriophage lambda (A.) and Ml 3 : linear DNA molecules, whose region can be replaced with foreign DNA without disrupting its life cycle; cloning limit: 8-20 kb. M13 is a filamentous phage which infects E-coli. Cloning limit: 10 kb.

Cosmids: A constructed extrachromosomal circular DNA molecule that combines features of plasmids and ‘cos’ site of phage ; cloning limit – 45 kb.

Yeast Artificial Chromosomes (YAC) : An artificial chromosome that contains telomeres, origin of replication, a yeast centromere, restriction enzyme site and a selectable marker for identification in yeast cells ; cloning limit: 1 Mb.

(c) Codon is a unit of genetic coding, consists of a series of three adjacent bases (triplet) in one polynucleotide chain of a DNA or RNA molecules, which codes for a particular amino acid during synthesis of proteins in a cell. For example, ATA codes for Leucine.

Start codon : The codon AUG specifies the first amino acid, methionine, in protein synthesis.

End codon : UAG also referred to as amber codon, in mRNA which terminate translation.

Question 3.  (ISC Biotechnology 2012 Class-12)
(a) Briefly explain the structure of a tRNA molecule. Mention its function during the process of protein synthesis. [4] (b) Give the stepwise procedure of sequencing of DNA by Sanger’s method. [4] (c) What is Totipotency ? Give an example of a Totipotent cell. [2] Answer 3:
(a) Transfer RNA (tRNA) : It is also called soluble or sRNA. There are over 100 types of tRNAs. Transfer RNA constitutes about 15% of the total RNA. tRNA is the smallest RNA with 70-85 nucleotides and sedimentation coefficient of 4S. The nitrogen bases of several of its nucleotides get modified e.g., pseudouridine (φ), dihydrouridine (DHU), inosine (I). This causes coiling of the otherwise single-stranded tRNA into L-shaped form (three-dimensional, Klug, 1974) or clover-like form (two dimensional, Holley, 1965). About half of the nucleotides are based paired to produce paired stems. Five regions are unpaired of single-stranded—AA-binding site, Tig C loop, DHU loop, extra arm and anticodon loop.

  • Anticodon. It is made-up of three nitrogen bases for recognizing and attaching to the codon of wRNA.
  • AA-Binding site. It lies at the 3′ end opposite to the anticodon and has CCA — OH group (5′ ends bears G). Amino acid or AA-binding site and anticodon are the two recognition sites of tRNA.
  • T φ C loop. It contains pseudouridine. The loop is the site for attaching to ribosomes,
  • DHU loop. The loop contains dihydrouridine. It is binding site for aminoacyl synthetase enzyme,
  • Extra arm. It is a variable site arm or loop which lies between T ig C loop and anticodon. The exact role of extra arm is not known.

tRNA is adapter molecule which is meant for transferring amino acids to ribosomes for synthesis of polypeptides. There are different tRNAs for different amino acids. Some amino acids can be picked up by 2-6 tRNAs. tRNAs carry specific amino acids at particular points during polypeptide synthesis as per codons of mRNA. Codons are recognised by anticodons of tRNAs. Specific amino acids are recognised by particular activating or aminoacyl synthetase enzymes,

They hold peptidyl chains over the mRNAs. The initiator tRNA has the dual function of initiation of protein synthesis as well as bringing in of the first amino acids. There is, however, no tRNA for stop signals.
ISC Biotechnology Question Paper 2012 Solved for Class 12 2
(b) DNA sequencing: It is the determination of the precise sequence of nucleotides in a sample of DNA.

Sanger dideoxy method: The most popular method for DNA sequencing is called the dideoxy method or Sanger method (named after its inventor, Frederick Sanger, who was awarded the 1980 Nobel prize in chemistry).

The Procedure : The DNA to be sequenced is prepared as a single strand.
This template DNA is supplied with

a mixture of all four normal (deoxy) nucleotides in ample quantities

  • dATP
  • dGTP
  • dCTP
  • dTTP

a mixture of all four dideoxynucleotides, each present in limiting quantities and each labeled with a tag.

  • that fluoresces a different color :
  • dd ATP
  • dd GTP
  • dd CTP
  • dd. TTP

DNA polymerase 1

Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxvnucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.

At the end of the incubation period, the fragments are separated by length from longest to shortest. The resolution is so good that a difference of one nucleotide is enough to separate that strand from the next shorter and next longer strand. Each of the four dideoxynucleotides fluoresces a different color when illuminated by a laser beam and an automatic scanner provides a printout of the sequence.

Limitation : Limitations include non-specific binding of the primer to the DNA, affecting accurate read-out of the DNA sequence, and DNA secondary structures affecting the fidelity of the sequence

(c) Cellular totipotency : Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism, including extraembryonic tissues and also the formation of a new organism. Totipotent cells formed during sexual and asexual reproduction include spores and zygotes.

Question 4.    (ISC Biotechnology 2012 Class-12)
(a) Briefly describe the essential components of the nutrient medium used for the plant tissue culture technique. Also, write the names of any two plant tissue culture media frequently used in the laboratory . [4] (b) With reference to suspension culture, explain the following : [4] (i) Achemostat.
(ii) A turbidostat.
(c) What are purines and pyrimidines ? Where are they located in a cell? [2] Answer 4:
(a) Nutrient Medium : Virtually all tissue culture media are synthetic or chemically defined; only a few of.them use complex organics, e.g., potato extract, as their normal constituents. A synthetic medium consists of only chemically defined compounds. A variety of recipes have been developed since none of them is suitable for either all plant species or for every purpose. Most of these recipes have been elaborated from those of White (itself evolved from a medium for algae) and Gautheret (based on Knop’s salt solution) The composition is as follow :

Inorganic nutrients: In addition to C, H and O, all nutrient media provide the 12 elements essential for plant growth, viz., N, P, K, Ca, S, Mg (these six are called macronutrients, and are needed in concentrations >0.5 mmol L-1 or > 0.5 mM), Fe, Zn, Mn Cu, B and Mo (these six are known a micronutrients, and are required in concentrations <0.5 mmol L” ’ ) Generally, iron is provided as iron.EDTAcomplex to keep it available at higher (>5.8) pH. Nitrate is superior to ammonium as the sole N source, but use of NH+ checks the drift of pH towards alkalinity.

Vitamins : For optimum callus growth, the following vitamins are required . inositol, thiamine, pyridoxine and nicotinic acid of which thiamine is essential and the rest are promotory. Pantothenic acid is also known to be promotory but is not included in most of the recipes.

Carbon source : Sucrose (20-50 g L) is the most commonly used carbon source for all cultured plant materials, including even green shoots. In some systems, e.g., monocots, glucose may be superior to sucrose. Plant tissue can utilize other sugars like maltose, galactose, lactose, mannose and even starch but these are rarely used.

Growth regulator: The following growth regulators (GRs) are used in plant tissue culture. Auxins, e.g., IAA (indole-3-acetic acid), IBA (indole-3-butyric acid), NAA (napthalene acetic acid), NOA (naphthoxy acetic acid), 2, 4-D (2,4-dichlorophenoxy acetic acid) etc., are commonly used to support cell division and callus growth (especially 2. 4-D), somatic embryo (SE) induction, rooting, etc. Cytokinins like kinetin (furfurylamino purine), BAP (benzylamino purine), zeatin, 2-ip (isopentenyl adenine), TDZ (thidiazuron, a compound having cytokinin activity) are employed to promote cell division, regeneration of shoots often SE induction and to enhance proliferation and growth of axillary buds. Abscisic acid (ABA) promotes SE and shoot bud regeneration in many species are markedly improves SE maturation. Of the over 20 gibberellins known, GA3 is almost exclusively used. It promotes shoot elongation and SE germination.

Complex organic additives: In earlier studies, complex additives like yeast extract, coconut milk, casein hydrolysate, com milk, malt extract and tomato juice are used to support plant tissue growth. White’s medium, Murashige and Skoog (MS) are the two common media used for plant tissue culture.


 (i) Chemostat :A type of cell culture; a component of medium is in a growth limiting concentration; fresh medium is added at regular interv als and equal volume of culture is withdrawn. But in a chemostat, a chosen nutrient is kept in a concentration so that it is depleted very rapidly to become growth limiting, while other nutrients are still in concentrations higher than required. In such a situation, any addition of the growth-limiting nutrient is reflected in cell growth. Chemostats are ideal for the determination of effects of individual nutrients on cell growth and metabolism.

(ii) Turbidostat: A type of suspension culture; when culture reaches a predetermined cell density, a volume of culture is replaced by fresh medium; works well at growth rates close to the maximum. A continuous culturing method where the turbidity of the culture is kept constant by manipulating the rate at which medium is fed. If the turbidity falls, the feed rate is lowered so that growth can restore the turbidity to its start point. If the turbidity rise the feed rate is increased to dilute the turbidity back to its start point.

(c) Purines and pyrimidines are two of the basic units of the nucleic acids. They are found in a DNA and RNA in a cell Purines is a large sized double ring structure. It contains two bases, i.e., adenine and guanine, Pyrimidines are small sized, single ring structures. It contains three type of bases i.e., thymine, cytosine and uracil.

Question 5.    (ISC Biotechnology 2012 Class-12)
(a) Explain giving an example how recombinant DNA technology can be used for the formation of
the following: [4] (i) A vaccine.
(ii) A plant with delayed fruit ripening.
(b) What is osmotic pressure ? Explain any one biochemical technique based on osmotic pressure. [4] (c) What are dextro-rotatory and laevo-rotatory substances? [2] Answer 5:

 (i) Recombinant vaccines : Vaccine is produced using recombinant DNA technology. A recombinant vaccine contains protein or a gene encoding a protein of a pathogen origin that is immunogenic A gene coding an immunogenic protein from the pathogen, is isolated, cloned and used for vaccine production The vaccines based on recombinant proteins are also called Sub-Unit Vaccines.

Whole protein vaccine : Hepatitis B vaccine is produced from surface antigens of transgenic yeast by r-DNA technology They can also be produced in genetically engineered microbes, cultured animal cells, possibly in insects and plants.

Recombinant – polypeptide vaccines : In some cases, the immunogenic portion of the protein- recombinant polypeptide is used as vaccine e.g., gene encoding B polypeptide (part of cholera enterotoxin – Ab A2 and B polypeptide) has been cloned and the recombinant B polypeptide produced is being used, in combination with inactivated cholera cells, as an oral vaccine in place of conventional injectable cholera vaccine. Immunogenicity of foot and mouth disease virus coat protein is due to its amino acids 114-160 and also 201 -213. They induce antibodies which neutralize the virus and thereby provide protection against the foot and mouth disease.

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