\n| (1) It stores data and programme temporarily.<\/p>\n (2) It contains the data of operating system, software’s and other application programmes.<\/td>\n | (1) It provides a non-volatile storage of data.<\/p>\n (2) It loads operating system into the memory and starts the computer when switched on.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n (b) (i) Glycine is the only amino acid which is optically inactive. It is the first neutral amino acid. In Glycine, the central atom has 2 hydrogen atoms. It does not contain any chiral carbon that\u2019s why it is optically inactive.
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/09\/ISC-Biotechnology-Question-Paper-2019-Solved-for-Class-12-1.png\") <\/p>\n (ii) Exponential Phase : It is a growth phase. In the exponential (log) phase, cells divide as fast as possible according to the growth medium, the microorganism itself and environmental conditions. This phase has a limited duration.
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/09\/ISC-Biotechnology-Question-Paper-2019-Solved-for-Class-12-2.png\")
\n(iii) Designer Oil : \u201cDesigner oil\u201d that reduces LDL ( bad ) blood cholesterol levels in humans and increases energy expenditure, which may prevent people from gaining weight. The oil incorporates a phytosterol-based functional food ingredient Phytrol (TM) from Forbes into oil using proprietary technology.<\/p>\n (iv) Palindromic sequence are the base pair sequences that are the same when read forward (left to right) or backward (right to left) from a central axis of symmetry. The sequences read the same on the two strands in 5 \u2192 3 direction and this is also true when we read in the 3 \u2192 5 directions.<\/p>\n (v) Colchicine is used in diploidization of haploid plants. There are mainly two approaches for diploidization-colchicine treatment and endometriosis.<\/p>\n (c) NBRI: National Botanical Research Institute
\nNBTB : National Biotechnology Board
\nBLAST: Basic Local Alignment Search Tool
\nPIR : Protein Information Resource
\nYAC : Yeast Artificial Chromosome<\/p>\n (d) (i) Callus : It is a mass of meristematic undifferentiated unorganized cells produced in a culture.<\/p>\n (ii) SNPs : Single Nucleotide Polymorphisms (SNPs) are the variations in a nucleotide at genomic DNA in different individuals at a population which occur due to change even in a single base (e.g., A, G, T or C). In human genome, SNPs occur at 1 n – 3.2 million sites.<\/p>\n (iii) Lyophilisation : In this method the microbial suspension is put in small ampoules and frozen through drying under vacuum. Vaccum drying results in sublimation of cell water. The lyophilised cultures are stored at 4\u00b0C. The culture remain viable for about 10 years. By this method a large number of cultures are maintained without variation in the characteristics.<\/p>\n (iv) Gene Cloning : It is a process of copying a specific desired gene\/section on DNA and producing in large number\/quantities.<\/p>\n (v) Cybrids : A cytoplasmicallv hybrid cell with organelles from both parental sources (obtained through fusion of cytoplast with a whole cell) and a nucleus of only one cell Nucleus of the other cell denatured.<\/p>\n Part – II (50 Marks)<\/strong>
\n(Answer any Jive questions)<\/strong><\/p>\nQuestion 2.
\n(a) With reference to composition of culture medium, answer the following : [4]
\n(i) Cytokinins
\n(ii) Auxin’s
\n(b) Explain the induced fit hypothesis of enzyme action with the help of suitable illustrations. [4]
\n(c) Write a note on Quaternary’ structure of proteins. [2]
\nAnswers:
\n(a) (i) Cytokinins:<\/p>\n \n- It stimulates the cell division process.<\/li>\n
- It helps in the morphogenesis of plant cell, along with auxins.<\/li>\n<\/ul>\n
(ii) Auxin:<\/p>\n \n- It helps in the formation of callus and in the development of xylem along with the promotion of cambial activity.<\/li>\n
- It is used for the elongation and enlargement of plant cell and it inhibits the promotion of growths of apical and lateral buds.<\/li>\n<\/ul>\n
(b) The Induced-fit theory:
\nThe key-lock hypothesis does not fully account for enzymatic action; i.e.. certain properties of enzymes cannot be accounted for by the simple relationship between enzyme and substrate proposed by the key-lock hypothesis. A theory called the induced-fit theory retains the key lock idea of a fit of the substrate at the active site but postulates in addition that the substrate must do more than simply fit into the already preformed shape of an active site.<\/p>\n Rather, the theory 7 states, the binding of the substrate to the enzyme must cause a change in the shape of the enzyme that results in the proper alignment of the catalytic groups on its surface. This concept has been likened to the fit of a hand in a glove, the hand (substrate) inducing a change in the shape of the glove (enzyme). Although some enzymes appear to function according to the older key-lock hypothesis, most apparently function according to the induced-fit theory .<\/p>\n Typically, the substrate approaches the enzyme surface and induces a change in its shape that results in the correct alignment of the catalytic groups. In the case of the digestive enzyme carboxypeptidase.
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/09\/ISC-Biotechnology-Question-Paper-2019-Solved-for-Class-12-3.png\")
\nThe induced-fit theory 7 explains a number of anomalous properties of enzymes. An example is \u201cnon-competitive inhibition.” in which a compound inhibits the reaction of an enzyme but does not prevent the binding of the substrate. In this case, the inhibitor compound attracts the binding group so that the catalytic group is too far away from the substrate to react. The site at which the inhibitor binds to the enzyme is not the active site and is called an allosteric site. The inhibitor changes the shape of the active site to prevent catalysis without preventing binding of the substrate. An inhibitor also can distort the active site by affecting the essential binding group: as a result, the enzyme can no longer attract the substrate.<\/p>\n (c) Quaternary Structure of proteins (4\u00b0 Structure) : It is the last or fourth level of protein organisation found in only oligomeric proteins or multimers. The multimeric proteins are formed of two to several poly peptides. The monomers or polypeptide sub units are also called protomers. Protomers maybe similar, e.g., two similar a polypeptides in enzyme phosphorvlase. It is known as homogeneous Quaternary structure. An oligomeric protein having dissimilar sub units shows heterogeneous Quaternary structure, .e.g., tetrameric hemoglobin with two ot (141 amino acids each) and two p (146 amino acids each) polypeptide chains.<\/p>\n Question 3.
\n(a) Explain the important postulates of central dogma. [4]
\n(b) Name and explain the method used to sterilize the following : [4]
\n(i) Vitamins
\n(ii) Forceps and Scalpels
\n(iii) Nutrient Media
\n(iv) Explant
\n(c) What is the Chargaff’s rule of equivalence ? [2]
\nAnswers:
\n(a) The \u2018Central Dogma\u2019 is the process by which the instructions in DNA are converted into a functional product. It was first proposed in 1958 by Francis Crick, discoverer of the structure of DNA.<\/p>\n 1. The central dogma of molecular biology explains the flow of genetic information, from DNA to RNA, to make a functional product, a protein.<\/p>\n 2. The central dogma suggests that DNA contains the information needed to make all of our proteins, and that RNA is a messenger that carries this information to the ribosomes .<\/p>\n 3. The ribosomes serve as factories in the cell where the information is \u2018translated\u2019 from a code into the functional product.<\/p>\n 4. The process by which the DNA instructions are converted into the functional product is called gene expression.<\/p>\n 5. Gene expression has two key stages – transcription and translation .<\/p>\n 6. In transcription, the information in the DNA of every cell is converted into small, portable RNA messages.<\/p>\n 7. During translation, these messages travel from where the DNA is in the cell nucleus to the ribosomes where they are \u2018read\u2019 to make specific proteins.<\/p>\n 8. The central dogma states that the pattern of information that occurs most frequently in our cells is :<\/p>\n \n- From existing DNA to make new DNA (DNA replication)<\/li>\n
- From DNA to make new RNA (transcription)<\/li>\n
- From RNA to make new proteins (translation)<\/li>\n<\/ul>\n
9. Reverse transcription is the transfer of information from RNA to make new DNA. this occurs in the case of retroviruses, such as HIV . It is the process by which the genetic information from RNA is assembled into new DNA.<\/p>\n Does the \u2018Central Dogma\u2019 always apply?<\/p>\n \n- With modem research it is becoming clear that some aspects of the central dogma are not entirely accurate.<\/li>\n
- Current research is focusing on investigating the function of non-coding RNA.<\/li>\n
- Although this does not follow the central dogma it still has a functional role in the cell.<\/li>\n<\/ul>\n
(b) Sterilization methods:
\n(i) Vitamins : Vitamins can be sterilize by the method of autoclaving. For this a concentrated stock solution is required to be prepared followed by fitration and subsequent addition in sterile medium at the temperature of growth (or room temperature).<\/p>\n (ii) Forceps & Scalpels : The metallic instruments like forceps, scalpels, needles, spatulas can be sterilized by flame sterilization method. For this we have to dip them in 25% ethanol ‘ followed by flaming and cooling. It is called incineration.<\/p>\n (iii) Nutrient media : Culture media are properly dispensed in glass container, plugged with cotton or sealed with plastic closures and sterilized by autoclaving (steam sterilization) at 15 psi for 30 minutes. Minimum temperature required for autoclaving of nutrient media is 15 minutes.<\/p>\n (iv) Explant: The explants are sterilized by disinfectants (e g., sodium, hypochlorite. NaOCl, mercuric chloride-HgCl2<\/sub>) and washed aseptically for 6-10 times with sterlized distilled water.<\/p>\n(c) Chargaff’s rule of equivalence : Deoxy ribonucleic Acid (DNA), the genetic material is made up of four types of organic nitrogenous bases : adenine (A), guanine (G), thymine (T) and cytosine (C). Of these, A and G are the purines and T and C are the pyrimidines. Chargaff gave the base pairing rule or the rule of base equivalence which states that only one purine can combine with one pyrimidine. That means A can combine with T and G with C. Two purines or two pyrimidines cannot combine with each other; if they do so, there w ill be a sudden change in the characteristic of an organism. This sudden change is called mutation.<\/p>\n Question 4,
\n(a) Differentiate between oils and fats. Discuss hydrolysis, rancidity and hardening shown by lipids. [4]
\n(b) Using tissue culture method one can produce disease free plants. Discuss the method used to produce virus free plants. [4]
\n(c) Write the main objectives of HGP. [2]
\nAnswer:
\n(a) Difference between Fats and Oils :<\/p>\n \n\n\n| Fats<\/td>\n | Oils<\/td>\n<\/tr>\n | \n| 1. Solid at room temperature<\/td>\n | 1. Liquid at room temperature<\/td>\n<\/tr>\n | \n| 2. Saturated and trans are its types<\/td>\n | 2. Unsaturated fats like monounsaturated and polyunsaturated are its types<\/td>\n<\/tr>\n | \n| 3. Mostly derived from animal<\/td>\n | 3. Mostly derived from plants<\/td>\n<\/tr>\n | \n| 4. Increases cholesterol levels<\/td>\n | 4. Improves cholesterol levels<\/td>\n<\/tr>\n | \n| 5. Mainly comes from animal food but also through vegetable oil by process called hydrogenation<\/p>\n Example: Butter, beef fat Contains 9 cal\/gm<\/td>\n | 5. Mainly comes from plants or fish<\/p>\n Example:Vegetable oil, fish oil Contains 9 cal\/gm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Hydrolysis of lipids: Hydrolysis is the breakdown of a substance by the addition of water. Fats and oils are hydrolyzed by moisture to yield glycerol and 3 fatty acids. This leads to hydrolytic rancidity of food product characterized by unpleasant flavor and aroma thereby making it undesirable for consumers. Chemically fats are esters, so they are liable to hydrolysis. This reaction is catalyzed by lipase enzyme or can occur via non-enzymatic hydrolysis. Partial hydrolysis of triglycerides will yield mono- and di- glycerides and free fatty’ acids.<\/p>\n Rancidity: Rancidity is the natural process of decomposition of fats or oils by either hydrolysis or oxidation or by both. The process of degradation converts fatty acids esters of oils into free fatty acids. This gives rise to an unpleasant odour and taste in food. These lipids degrade to the point of becoming either unpalatable or unhealthy to ingest.<\/p>\n Hydrogenation and hardening: Hydrogenation of unsaturated fatty acids is widely practiced. This treatment affords saturated fatty acids. The extent of hydrogenation is indicated by the iodine number. Hydrogenated fatty- acids are less prone toward rancidification. Since the saturated fatty acids are higher melting than the unsaturated precursors, the process is called hardening.<\/p>\n (b) Production of virus-free plants : Plant viruses are found in nature and propagate inside the cells of living plant. There are many plants that suffer from serious diseases developing a variety of symptoms such as mosaic, chlorosis, necrosis, vein clearing, lead curling, leaf rolling, etc. Sometimes the disease severity is so high that viruses migrate to vascular bundles and also get established inside the seeds.<\/p>\n For the first time G Moral and C. Martin (1952) produced virus-free shoots of Dahlia from virus-infected plants through shoot meristem culture, On 26th November, 2002 a US Patent was granted to H.C. Chaturvedi and co-workers for successfully regenerating and proliferating shoot meristem of Cirus spp.<\/p>\n Using tissue culture method we can produce disease-free plants. Generally, the apical meristem of plants are free from viruses and the other microorganisms. However, if viral particles are present, their number would be quite low.<\/p>\n Methods of virus elimination :
\nThere are two methods that are used to produce virus-free plants.
\n(i) Heat Treatment of Meristem : Before meristem culture, viruses associated with meristem are eliminated in vitro by heat treatment (thermotherapy) of whole plants. Heat treatment is given through hot water or air at 35-40\u00b0C for a varying period (a few minutes to several months). It should be noted that prolonged heat treatment inactivates that host resistance. Percentage of plant survival is also low. Temperature tolerant viruses may survive inside the plant tissue.<\/p>\n (ii) Meristem-tip Culture : Meristem-tip culture is the most widely applicable approach for virus elimination. In most of the cases explant (shoot tip) of 100-1000 pm has been cultured to raise virus-free plants. But the explant of small size (1 mm) i.e., meristem tip is preferred for in-vitro culture. Meristem tip is excised in aseptic conditions and cultured on nutrient medium. If required thermotherapy is given to the mother plant before excision of meristem tip. The inoculated tubes are incubated properly in light and dark regime (Fig.)<\/p>\n There are some chemicals which are used to eliminate viruses from plant tissues and protoplasts. These are malachite green, thiouracil, acetyl salicylic acid, cycloheximide, actinomvcin-D, etc.
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\n(c) Objectives of HGP :
\n(1) The goals of the original HGP were not only determine all 3 billion base pairs in the human genome with a minimal error rate, but also to identify’ all the genes in this vast amount of data. This part of the project is still ongoing although a preliminary count indicates about 30,000 genes in the human genome, which is far fewer than predicated by most scientists.<\/p>\n (2) Another goal of the HGP was to develop faster and more efficient methods for DNA sequencing and sequence analysis and the transfer of these technologies to industry.<\/p>\n (3) Another goal of the HGP is the study of its ethical, legal, and social implications. It is important to research these issues and find the most appropriate solutions before they become large dilemmas. Otherwise its effect will manifest in the form of major political concerns.<\/p>\n Question 5.
\n(a) Discuss the mechanism of the lac operon model of regulation of gene expression. [4]
\n(b) Give four points of difference between southern blotting technique and northern blotting technique. [4]
\n(c) Give four characteristics of genetic code. [2]
\nAnswers:
\n(a) The lac Operon Model: The lac operon model is an example of transcriptional regulation of gene expression. The lac operon consists of a promoter, an operator and three structural genes (Fig.). RNA polymerase binds to promoter site of DNA. This result in start of sequential transcription of structural genes (lac Z, lac Y and lac A). The lac Z expresses gene \u03b2-galactosidase, lac Y encodes permease and lac A synthesizes transacetylase. The operator site is located between the promoter and first structural gene (lac Z). The repressor protein, expressed by the regulator gene, binds to operator. The structural gene (lac Z. lac Y and lac A) do not express enzymes (A).
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2019\/09\/ISC-Biotechnology-Question-Paper-2019-Solved-for-Class-12-5.png\")
\nThe repressor protein expressed by the repressor gene (which is not a part of operon) involves the transcription of structural genes. Transcription of structural genes is stopped when repressor protein is attached on the operator gene. If lactose is supplied, it enters the cell and binds with repressor protein. Then repressor protein is inactivated due to change in conformation of the repressor protein. Therefore, repressor fails to attach on the operator gene, and the structural genes are transcribed into an wRNA which in turn translates the proteins (B).<\/p>\n Here, lactose acts as anti-inducer but not a real inducer. Allolactose (an inducer of lactose) is a natural inducer for the lac operon. In regulation of lac operon, lactose is taken up. Then it is broken by p-galactosidase into glucose and galactose. Galactose is converted into allolactose and lactobiose through a side reaction with lactose. The allolactose induces the operon. Consequently, lactose is utilized enzymatically.<\/p>\n (b) Southern Blotting technique involves separation and identification of a specific DNA fragment. In Northern Blotting technique, the RNA is analysed rather than DNA. During southern blotting NaOH denatures DNA to form single stranded DNA which are transferred from gel to nitrocellulose membrane. In northern blotting, total RNA molecules are extracted and then mRNA molecules are isolated by using oligo (dT) cellulose Chromatography. RNA samples separated are transferred to a nylon membrane.<\/p>\n (c) Characteristics of Genetic Code :
\n(i) Triplet code : Three adjacent nitrogen bases constitute a codon which specifies the placement of one amino acid in a polypeptide.<\/p>\n (ii) Start signal: Polypeptide synthesis is signaled by AUG or methionine codon and GUG \u2014 Valine codon. They have dual function.<\/p>\n (iii) Stop signal: Polypeptide chain termination is signaled by three termination codons \u2014 UAA, UAQ and UGA. They do not specify any amino acid and are hence also called non-sense codon.<\/p>\n (iv) Universal code : The genetic code is applicable universally i.e. the codon specifies the same amino acid from a virus to a tree or human being.<\/p>\n (v) Non-ambiguous codon : One codon specifies only one amino acid and not any other.<\/p>\n Question 6.
\n(a) With reference to vector less methods of gene transfer explain each of the following : [4]
\n(i) Liposome mediated gene transfer
\n(ii) Electroporation
\n(iii) Transfection
\n(iv) Transformation
\n(b) With reference to application of tissue culture techniques, explain the following : [4]
\n(i) Haploid production
\n(ii) Triploid production
\n(c) What is meant by DNA probe ? [2]
\nAnswers:
\n(a) The term direct or vector less transfer of DNA is used when the foreign DNA is directly introduced into the plant genome. Direct DNA transfer methods rely on the delivery of naked DNA into the plant cells. This is in contrast to the Agrobacterium or vector-mediated DNA transfer which may be regarded as indirect methods. Majority of the direct DNA transfer methods are simple and effective. And in fact, several transgenic plants have been developed by this approach.<\/p>\n 1. Liposome-Mediated Transformation: Liposomes are artificially created lipid vesicles containing a phospholipid membrane. They are successfully used in mammalian cells for the delivery of proteins, drugs etc. Liposomes carrying genes can be employed to fuse with protoplasts and transfer the genes.The efficiency of transformation increases when the process is carried out in conjunction with polyethylene glycol (PEG). Liposome-mediated transformation involves adhesion of liposomes to the protoplast surface, its fusion at the site of attachment and release of plasmids inside the cell.<\/p>\n 2. Electroporation: Electroporation basically involves the use of high field strength electrical impulses to reversibly permeabilize the cell membranes for the uptake of DNA. This technique can be used for the delivery of DNA into intact plant cells and protoplasts. The plant material is incubated in a buffer solution containing the desired foreign\/target DNA, and subjected to high voltage electrical impulses. This results in the formation of pores in the plasma membrane through which DNA enters and gets integrated into the host cell genome.<\/p>\n 3. Transfection: Transfection is the process of inserting genetic material, such as DNA and double stranded RNA, into mammalian cells. The insertion of DNA into a cell enables the expression, or production of proteins using the cell\u2019s own machinery, whereas insertion of RNA into a cell is used to down-regulate the production of a specific protein by stopping translation. While the site of action for transfected RNA is the cytoplasm, DNA must be transported to the nucleus for effective transfection. Therefore, the DNA can be transiently expressed for a short period of time, or become incorporated into the genomic DNA, where the change is passed on from cell to cell as it divides.<\/p>\n 4. Transformation: Transformation is the method of introducing foreign DNA into bacterial cells (e.g. E.coli). The uptake of plasmid DNA by E.coli is carried out in ice-cold CaCl2<\/sub> (0-5\u00b0C), and a subsequent heat shock (37-45\u00b0C for about 90 sec). By this technique, the transformation frequency, which refers to the fraction of cell population that can be transferred, is reasonably good e.g. approximately one cell for 1000 (10-3) cells.The mechanism of the transformation process is not fully understood. It is believed that the CaCl2<\/sub> affects the cell wall, breaks at localized regions, and is also responsible for binding of DNA to cell surface. A brief heat shock (i.e. the sudden increase in temperature from 5\u00b0C to 40\u00b0C) stimulates DNA uptake. In general, large-sized DNAs are less efficient in transforming.<\/p>\n(b) (i) Applications of triploid plants :<\/p>\n | |
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