eChapters

1 Professor (Retired) Department of Agricultural Extension and Rural Sociology, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu

2 Assistant Professor, Department of Agricultural Extension and Rural Sociology, Agricultural College & Research Institute, Madurai-625 104

Introduction

The word ‘Extension’ was first coined in U.S.A. in the mid-part of the nineteenth century, to connote extension knowledge of improved practices in agriculture and home economics from Land Grant Colleges to the farmers and their families in their fields and homes. The literary meaning of Extension is ‘Ex’-out; Tensio’-to stretch i.e. Extension means stretching out. Extension, in the context of rural community development, means educating rural people and it implies production of changes in human behaviour -in terms of attitude, knowledge and skill. Extension is often misconceived as disbursement of subsidies and providing certain material incentives; it is certainly not.

There are several conventional extension techniques approaches and tools for transfer of any farm -related technologies, be it any enterprise, crop or their mix. Extension teaching aids are broadly classified as:

1 & 3 Assistant Professor, Dept. of Agricultural Extension and Rural Sociology, Agricultural College & Research Institute, Tamil Nadu Agricultural University, Madurai -625 104

2 & 4 Senior Research Fellows, Dept. of Agricultural Extension and Rural Sociology, AC & RI, Madurai -625 104.

Prelude

The rapid and unprecedented changes in the external environment such as liberalisation of the economy, globalisation of international markets, deregulation of the financial systems and implications of various clauses under WTO exerted considerable pressure on the agricultural system. Moreover, the major challenges facing the world today includes are: managing the environment in a sustainable manner, managing the exploding rate of population growth and urbanisation, ensuring food security, meeting health, education and literacy needs and eliminating poverty.

Meeting these challenges requires information, knowledge and participatory process of social change. Communication is an essential element in this process. According to Balit (1996) who pointed out that least expensive input for rural development is knowledge. Knowledge and information are basic ingredients of food security and are essential for facilitating rural development and bringing about social and economic change.

The 21^st century is witnessing a computer revolution in which information processing and retrieval are being reliably done at incredible speeds. Computers are used for storing, analysing and distributing information of all kinds including words, numbers, pictures, illustration, sounds and movies. Computer aided knowledge dissemination mechanism help to reach the unreached and foster new voices and new leaders.

According to Aasher (1995) microcomputer technologies have the potential to support all the major functions of agricultural extension, namely the technology generation, diffusion, adoption continuum and the efficient handling of descriptive, diagnostic, predictive and prescriptive types of information.

My definition of a ‘Developed India’ is “when the quality of life in our rural areas becomes comparable to that in the non-urban areas of already developed countries”. Another way of looking at development is to look at ‘Measures of Development’. Unlike the three used by United Nations, viz. per-capita Gross National Product, life expectancy at birth and adult literacy, I have been suggesting for a long time that the appropriate measures of development for a developing country are only two – per capita electricity consumption and female literacy. Availability of electricity is essential to provide the basic amenities like pure drinking water and proper health care and to develop rural industries. And also, without near-hundred per cent literacy and without societal equity – evidenced inter-alia through gender non-discrimination – the fruits of science and technology (S&T) will not fully reach rural India.

Technology Foresight to Become a ‘Developed’ Country

Choosing the right technologies to put the nation on the part of rapid development requires technology Foresight. Technology foresight must be distinguished from Technology Forecasting, which attempts to predict future technological developments, without worrying about the impact of these developments on the economy, society or the environment. Technology foresight adds assessments from economic, social, environmental, security and even ethical points of view to technology foresight. One may often get different answers from such analysis depending on whether you are from India or say, from the United States of America, to the need for technologies like, for example, fast breeder reactors or rural food processing.

What is an IVR

IVR or Interactive Voice Response is a technology that automates interaction of a database with telephone callers. Enterprises are increasingly turning to IVR to reduce the cost of common sales, service, collections, inquiry and support calls to and from their company.

IVR solutions are generally used with pre-recorded voice prompts and menus to present information and options to callers, and touch-tone telephone keypad entry to gather responses. Modern IVR solutions however, also enable input and responses to be gathered via spoken words with voice recognition.

IVR solutions enable users to retrieve information including bank balances, flight schedules, product details, order status, movie show times, and more from any telephone. Additionally, IVR solutions are increasingly used to place outbound calls to deliver or gather information for appointments, past due bills, and other time critical events and activities.

History

Video conferencing uses telecommunications of audio and video to bring people at different sites together for a meeting. This can be as simple as a conversation between two people in private offices (point-to-point) or involve several sites (multi-point) with more than one person in large rooms at different sites. Besides the audio and visual transmission of people, video conferencing can be used to share documents, computer-displayed information, and whiteboards.

Simple analog videoconferences could be established as early as the invention of the television. Such videoconferencing systems consisted of two closed-circuit television systems connected via cable. During the first manned space flights, NASA used two radiofrequency (UHF or VHF) links, one in each direction. TV channels routinely use this kind of videoconferencing when reporting from distant locations, for instance. Then mobile links to satellites using special trucks became rather common.

This technique was very expensive, though, and could not be used for more mundane applications, such as telemedicine, distance education, business meetings, and so on, particularly in long-distance applications. Attempts at using normal telephony networks to transmit slow-scan video, such as the first systems developed by AT&T, failed mostly due to the poor picture quality and the lack of efficient video compression techniques. The greater 1 MHz bandwidth and 6 Mbit/s bit rate of Picture phone in the 1970s also did not cause the service to prosper

Access to information and improved communication is a crucial requirement for sustainable agricultural development. Modern communication technologies when applied to conditions in rural areas can help improve communication, increase participation, disseminate information and share knowledge and skills. It is being said that “Cyber Extension” would be the major form of technology dissemination in the near future. However it is observed that the rural population still have difficulty in accessing crucial information in order to make timely decisions. It is essential that information availability is demand driven rather than supply driven. The challenge is not only to improve the accessibility of communication technology to the rural population but also to improve its relevance to local development.

The advent of INTERNET on communication scenario offers enormous potential for two-way on-line communication between distant parties via the telecommunication and computer network spread over the entire globe. The world is rapidly shrinking to a ‘global village’ which some courageously even call a ‘global family’. The merger of communication (audio and video) and computer technology has suddenly made this combination so powerful that no sector of human activity can afford to ignore it. Right from high security defense systems, space research, engineering and educational applications the INTERNET has found users in petty shopkeepers and small service agencies. In countries like Singapore, you can book a taxi via e-mail and the concerned taxi driver is able to confirm your booking, while he is still driving.

Introduction

Expert system can be defined as a tool for information generation from knowledge. Information is either found in various forms or generated from data and/or knowledge. Text, images, video, audio are forms of media on which information can be found, and the role of information technology is to invent, and devise tools to store and retrieve this information. Statistical information is a good example of information generated from data while advises generated by an expert system is a good example of information generated from knowledge.

At the beginning, the concentration was mainly on textual information. Information technology used for textual information ranged from paper archiving tool to the sophisticated electronic computer software tools such as data base management systems, and hypertext tools. Images were very difficult to be included in an information system just few years ago till the scanners technology has been advanced together with the invention of the optical storage devises which have the capacity to store hundreds of mega bytes. This technology has enabled the developers to include images in their systems. Input peripherals to capture video and audio information have been also commercialized and are now available in the market. Storage of audio and video would be impossible unless large storage media were invented.

ABSTRACT

An Expert System also called a Knowledge Based System is a computer program designed to simulate the problem-solving behavior of an expert in a narrow domain or discipline. In agriculture, expert systems unite the accumulated expertise of individual disciplines, e.g., plant pathology, entomology, horticulture and agricultural meteorology, into a framework that best addresses the specific, on-site needs of farmers. Expert systems combine the experimental and experiential knowledge with the intuitive reasoning skills of a multitude of specialists to aid farmers in making the best decisions for their crops. The various expert systems were developed since evolution of Artificial Intelligence. This paper compares the availability of various expert systems in agriculture for last 30 years.

Introduction

Agricultural production has evolved into a complex business requiring the accumulation and integration of knowledge and information from many diverse sources. In order to remain competitive, the modern farmer often relies on agricultural specialists and advisors to provide information for decision making. Unfortunately, agricultural specialist assistance is not always available when the farmer needs it. In order to alleviate this problem, expert systems were identified as a powerful tool with extensive potential in agriculture.

Introduction

Precision farming is one of the most scientific and modern approaches to sustainable agriculture that has gained momentum in 21^st century. Consider this situation: ‘A farmer goes to his field with his GPS (Global Positioning System) guided tractor. The GPS senses the exact location of the tractor within the field. It sends the signal to a computer on the tractor, which has a GIS, storing the soil nutrient requirement map in it. The GIS, in consultation with a Decision Support System, decides what is the exact requirement of the fertilizer for that location and then commands a variable rate fertilizer applicator, attached with the tractor, to apply the exact dose at that precise location. And all this is done within a second, before the tractor moves further.’ Sounds like an excerpt from a scientific fiction. But this is what precision farming (PF) means to the large growers of the US or European countries. Hence, the first thing that comes to mind is that, this system is not for developing countries, especially India, where the farmers are poor, farming is mostly subsistent and the land holding size is small. But, this is far from the truth as this approach has a large potential for improving the agricultural production in developing world. This article is an attempt to explain the possibility of adopting PF in India and the role of satellite based remote sensing in facilitating that.

Introduction

Over the last two decades the Land and Water Development Division (AGL) has been at the forefront of the development and application of computer-based systems to analyse data and generate information to support decisions on various land and water issues . Separate soil and land and water systems have been developed. The soil and land systems focus on methodologies and tools for the assessment of land resources potentials at global, regional and national and sub-national levels. The water systems concern irrigation water use and management at field level and water resources assessment at regional and national levels.

AGL has been cooperating with various units within FAO and numerous international agencies and national institutions in developing and applying the systems.

Initially, in the late seventies and early eighties, the systems were developed for mainframe and mini-computers. From the late eighties they were gradually adapted to microcomputers. At the same time computer tools for managing spatial data, including geographic information systems (GIS), remote sensing and global positioning systems (GPS) were introduced. Since the last few years the availability of networked PC workstations, rapid application development environment and multimedia tools have opened an era of completely new possibilities in the development and application of the systems.

ABSTRACT

Indian farming community is facing a multitude of problems to maximize crop productivity. In spite of successful research on new agricultural practices concerning crop cultivation, the majority of farmers is not getting upper-bound yield due to several reasons. One of the reasons is that expert/scientific advice regarding crop cultivation is not reaching farming community in a timely manner. It is true that India possesses a valuable agricultural knowledge and expertise. However, a wide information gap exists between the research level and practice. Indian farmers need timely expert advice to make them more productive and competitive. In this paper, we made an effort to present a solution to bridge the information gap by exploiting advances in Information Technology (IT). We propose a framework of a cost-effective agricultural information dissemination system (AgrIDS) to disseminate expert agriculture knowledge to the farming community to improve the crop productivity. Some of the crucial benefits of AgrIDS are as follows. It is a scalable system which can be incrementally developed and extended to cover all the farmers (crops) of India in a cost effective manner. It enables the farmer to cultivate a crop with expertise, as that of an agricultural expert, by disseminating both crop and location specific expert advice in a personalized and timely manner. With AgrIDS, the lag period between research effort to practice can be reduced significantly. Finally, the proposed system assumes a great importance due to the trend of globalization, as it aims to provide expert advice which is crucial to for the Indian farmer to harvest different kinds of crop varieties based on the demand in the world market.

Introduction

Information technology is rapidly changing the use of Geographic Information Systems (GISs) from the classic desktop applications into the business service market. With the ubiquitous computing, the settings change dramatically and the classic GIS market will change drastically in the coming few years.

Till mid 90’s, the architecture of GIS focused on a standalone (static) environment. This architecture has been changed to move GIS applications from workstations into mobile GIS applications.

Mobile map applications is not a conventional GIS modified to operate on mobile devices, but a system build using a fundamentally new paradigm(Maguire,2001).

In this paper, we will discuss the integration of XML (eXtensible Markup Language) and J2ME (Java 2 Micro Edition) to build a mobile map application running on 2.5G and 3G mobile devices such as Nokia series 60.

ABSTRACT

Over the last three decades, SAC has been engaged in the development and dissemination of remote sensing and GIS technologies for national development. These developments have originated from various initiatives related to national projects, sensor related research and in-house research and development on applications. A large multidisciplinary team of scientists develop technologies in various fields of applications like agriculture, coastal zone management, urban planning, forest and environment, etc. In addition, significant efforts are directed towards technology development for generic applications like photogrammetry and applications involving synergistic usage of remote sensing, GIS, GPS and satellite communication. Some specific examples of recent technological developments pertain to simulation modeling of crop yields, horticultural crop management, site selections for aquaculture, location of cold storage plants, large area crop production forecasting, base map creation, telegeoprocessing, mobile satellite services for fleet management, automated procedures for linear infrastructure planning, urban land use allocation planning.

An overview of these technologies and the modalities for their effective utilization by government, industries and users are summarized. Dissemination of these technologies for public bodies and private sector has been taken in the form of promotion of consultancy services in different application areas. Some major areas where these sectors have benefited through consultancies are estimation of cash and other field crops, city development planning, site selection for industry, land use change detection studies for environmental impact assessment, coastal regulation zone compliances and land use scenario, forestry related applications like catchment area treatment, forest fires monitoring, etc. Examples of consultancy services for private sector are included.

Keywords : Technology dissemination, technology development, remote sensing applications.

ABSTRACT

Dairy Development plays a vital role in bringing out significant changes in socio-economic structure of rural economy. The main objectives of Dairy Developments in India is to increase production and availability of milk through integrated policy of cattle cum Dairy Development, eliminating the middlemen, through formation of co-operatives and self supporting dairy enterprise. The advent of Geographical Information System (GIS) has added new vistas in the field of Dairy Farm and Management. It also helps in integrating the whole Dairy Farm in a more precise way to get correct information about the various factors related with the whole dairy farm.

Introduction

The farm of Sarasa Green Projects around Chapabandi, Bansgora and Hetedoba Mouzas near Durgapur in Burdwan District of West-Bengal. Dairy Development plays a vital roll in brining about significant changes in socio-economic structure of rural economy. The main objectives of Dairy development in West-Bengal is to increase production and availability of milk through integrated policy of cattle cum Dairy Development eliminating the middlemen through formation of co-operatives and self supporting dairy enterprise. (Fig.1)

Asia-Pacific Association of Agricultural Research Institutions (APAARI) Maliwan Mansion, 39 Phra Atit Road, Phra Nakorn, Bangkok 10200, Thailand

Selected ICT-enabled Agricultural Development Initiatives

• International Initiatives
• National Initiatives

Success Stories on Agricultural Information Systems

• South Korea’s Agricultural Information Service – A NARS Initiative
• ITC’s e-Choupal – A Private Sector Initiative

Lessons Learned on Secrets of Success

Extent of Adoption of Technology

Benefits and Impact at National and Regional Levels

Background

Context

The information and knowledge system in virtually all sectors and access during the Soviet period was strictly state controlled and was essentially designed to meet the requirements of centralized planning. Very little information sourcing, message development, media packaging took place at the local level. Requirements for meeting agricultural production quotas were channeled to Moscow where information packages and norms, based on a central assessment of local needs were developed and transmitted from the center directly to the state and collective farms. The information was disseminated primarily via dense print publications, radio, TV, public campaigns, exhibitions and fairs, and to some extent through a computer network to areas with functioning telecommunication systems. The types of information and knowledge which the state and collective farms, private farmers, kitchen gardeners, agro-processing industries, input suppliers, marketing institutions and others engaged in agriculture could obtain were restricted and opportunities for exchange with the rest of the world were extremely limited and tightly controlled. There were very few avenues for cross checking the information received. In-house, well trained technical specialists addressed a variety of crop and livestock related problems and served as the main providers of knowledge. This was supplemented by research and field applications through a very large network of a variety of agricultural research institutes and experiment stations. Most of the research results were introduced through directives. Linkages between education, research, extension and end-users were weak and in some areas non-existent. However, the importance placed on education and training of all Soviet citizens resulted in a highly literate population to serve the needs of a socialistic economy. The centralized information and knowledge system was primarily aimed at meeting production targets in the plan with little or no importance placed on economic or environmental sustainability of farming systems and development of agro-industries.

Introduction to DHAN Foundation

DHAN (Development of Humane Action) Foundation is a grassroots action agency working with poor communities in villages. Enhancing poor people’s livelihoods in sustainable way and enabling the poor communities are the focus of the programmes. The mission of the organisation is to build institute for innovation in the development work and reaching significance to bring positive changes in the lives of poor. DHAN Foundation was established in year 1997 as spin off institution of PRADAN (Professional Assistance for Development Action) based at New Delhi.

DHAN Foundation believes in building the capacity of people in planning, organizing, conflict resolution and implementation of development programmes. This will be possible only when people are encouraged to work on a single thematic focus, either through micro finance or small scale irrigation theme, for a substantive period to pick-up the generic skill of developing viable alternatives to their stalemate situation; DHAN Foundation initiatives are aimed at building people constituencies around specific activity, these institution will move into civic programmes like health, Education and Information Technology to address their member’s needs. Simultaneously DHAN Foundation as a mothering institution promotes thematic organizations as subsidiaries to upscale the matured themes and continue the promotional role to sustain the people’s organization in the specific theme for e.g. micro finance or irrigation.

Introduction

Growth of Science is never ending process. In that, technology development is dynamic in nature. It is applicable to all the fields come under the Science, including Agriculture also. Continuous evaluation of improved technologies had taken place in Agriculture. On the other hand, communication network through Cyber techniques or E-Extension plays a crucial role. By the way, there is a need of innovative approaches for effective technology transfer for which no one is clear like that of deriving new technologies. Starting from the 20^th century, many programmes were launched for development of rural India. As these were official dominated and top-down system, the ‘Panchayati Raj’ -the three-tier system was introduced at village, block and district levels in 1960’s keeping the local leaders as Kingpins with more participation of rural people. This had also not given due dividends owing to political infiltration and less co-operation by the development departments and lack of coordination among all concerned. A panoramic view of extension world over gives varieties of models and experiences. But no single model would suit to our conditions and here we need louder thinking on this line.

This book is designed to introduce to the students some of the most widely used experimental procedures in biotechnology, including DNA/RNA isolation, manipulation, cloning, protein purification and characterization. The students will also get familiarized with some of the equipments frequently used in biochemistry and molecular biology.

The biotechnology laboratory course is an exploration of procedures. Hence, in order to get full benefit from the course, the students need to read the manual, which is self explanatory. The more effort they put into the course work, the more they will learn. Before the start of actual lab works, one needs to spend some time reading the Laboratory Manual. This reading will provide background information and an outline of the procedures to be performed.

The biotechnology laboratory is conducted as a “directed” research project. This means that although the general procedures are well established, the overall goal of each experiment is the acquisition of new information. Because of the nature of scientific research, predicting the outcome of experiments that have not previously been performed is difficult. It may therefore be necessary to design new experiments based on the results of previous ones, or to repeat experiments that yielded uninterruptable or ambiguous results.

In molecular biology and biochemistry, the ability to accurately and reproducibly measure and transfer small volumes of liquids is critical for obtaining useful results. For volumes less than 1 ml, the most common method for measuring liquid volumes involves the use of a device known as a pipetman or micro-pipette.

The pipetmen can be both fixed and variable volumes. Commonly used pipetmen are: P1000, P200, P20, P10 etc. P1000 are useful for volumes from 200 to 1000 µl. P200 are useful for volumes from 20 to 200 µl. P20 are useful for volumes from 0.5 to 20 µl. For beginners fixed volume pipetmen are more useful. It is important to ascertain whether the correct pipetman is chosen for measuring the volume one needs.

A spectrophotometer is an analytical instrument that measures the absorbance of a test sample (solution). The term “spectroscopy” comes from the word “spectrum”. “Spectroscopy” therefore implies the use of multiple wavelengths of light. Spectrophotometers have the ability to specifically measure absorbance at specific wavelengths. The most commonly used method to allow this involves a “monochromator”, a device (either a prism, or more commonly, a diffraction grating) that splits the incident light into its component wavelengths, and allows only light of the desired wavelength to reach the sample. The ability to measure absorbance at different wavelengths is very useful, because the extinction coefficient of a compound varies with wavelength. In addition, the absorbance spectrum of a compound can vary depending on the chemical composition of the compound, and depending on the nature of the solvent around the compound.

Absorbance is a useful quantity and follows the Beer-Lambert law. The extinction coefficient of a molecule at a given wavelength can be calculated using the Beer-Lambert equation from absorbance measurements for solutions of known concentration, which states that:

To prepare a series of dilutions of the original more concentrated stock solution, one need to consider both the required final concentration and required volume of the diluted material. The dilution can be readily calculated by the equation:

Several substrates, like proteins (enzymes), are very sensitive to alteration in the concentration of the solution they are placed in. Hence is the importance of a buffer which controls the chemical properties of the medium. Literally a “buffer” has the ability to resist changes in the hydrogen ion concentration. Although, buffers do contain other molecules, that might, in addition to the hydrogen ion concentration, influence the ionic strength, the activity of enzymes, and other parameters of the experiment.

In any biological experiment, appropriate buffer must be selected based on their effect on the experiment. Ideal buffers control pH and ionic strength without interacting adversely with the experiment undertaken. For example, although phosphate is a common buffer, it may not be suited when phosphate is a substrate or product of the reaction being studied. Also, some proteins interact poorly with some buffers. For example, Tris is not ideal as it exhibit high pKa and the large change in pKa when temperature changes, although it is cheap and most proteins are stable in Tris buffers, moreover it seldom reacts with reaction substrates hence, Tris buffer is commonly used in biochemical experiments.

Autoclave Operating Procedures

Place all material to be autoclaved in an autoclavable tray. All items should have indicator tape. Separate liquids and solids should be autoclaved separately. Ensure that the lids on all bottles are loose. Do not put a large number of items in tray, to ensure that all items reach the appropriate temperature. Also allow sufficient air/steam circulation.

Steps in autoclave

Pressure should read ‘O’ when you open the pressure chamber of the autoclave.

Place items to be autoclaved in the autoclave and close the door. Some autoclaves require that you also lock the door after it’s closed.

Set time - typically 20 minutes.

Temperature should be set at 121°C already, but double-check and change if necessary.

Set cycle: If liquid, set “liquid cycle” or “slow exhaust”. If dry, set “dry cycle” or “fast exhaust” + dry time.

Start the cycle. On some autoclaves, the cycle starts automatically at step 5. On others, turn to “sterilize”

Storage

Nucleic acids are very sensitive to contaminations hence care should be taken while processing and storing DNA and RNA. The following properties of reagents and conditions need to be taken care of:

Heavy metals cause breakage of phosphodiester linkage. One can use EDTA which is an excellent heavy metal chelator.

UV rays cause extensive damage to nucleic acids. UV light at 260 nm causes breakage of thymine dimers and cross-link, including loss of biological activities.

Ethidium bromide results in photo oxidation of DNA. Oxidation products can cause phosphodiester breakage.

Nucleases are found on human skin; therefore, it is advisable to avoid direct or indirect contact between nucleic acids and fingers.

Most DNAes are not very stable; however, many RNAses are very stable and can absorb to glass or plastic and remain active.

At -20°C: extensive single and double strand breaks results. Hence for long-term storage it should be stores at -70°C. ? It is best to store DNA in high salt ( >1M) in the presence of high EDTA (>10mM) at pH 8.5, for long-term storage.

Storage of DNA in CsCl with ethidium bromide in the dark is an excellent storage medium. There is about one phosphodiester break per 200 kb of DNA per year.

Storage of ë DNA in the phage is better than storing the pure DNA.

Cell Genotypes

A large variety of bacterial strains, like E. coli, are frequently used in molecular biological experiments. Students should choose the strain or strains required for an experiment on the basis of genetic properties of the strains. It is thus pertinent that a sound knowledge of the genetic makeup of the E. coli stains is acquired.

The genetic makeup of the strains of E.coli is distinctly different from the wild type (K12 or B strains) strains from which they are derived and contains genes that can be modified. Genes are supposed to be mutated when they are not listed in a genotype. In most cases, the genes listed are mutated to the point of inactivity. In a few cases, a “-” (indicating inactive or absent or deleted), “+” (indicating active). , The genotype is a factor in choosing a bacterial strain. Chosen strains should be ascertained for their utility for the specific experiment.

Small Scale Cultures

Fresh culture from a freshly streaked plate should be taken while experimenting with E. coli cells. For preparing a small scale culture of E. coli , prepare 3-5 ml of LB medium/broth (or appropriate broth include antibiotic if the culture contains a plasmid) in two sterile 50 ml tubes. Inoculate one tube with a single colony from a fresh plate. The second tube is used as a broth control. Incubate both tubes at 37°C, shaking vigorously overnight. Inspect the tubes the next morning. The broth control should be clear and the inoculated culture should be very turbid. Make a note of any debris found in the tubes and only incubate longer if the culture is not dense. Never allow cells to overgrow. For some applications, cells can be stored at 4°C for short periods prior to use.

PCR Principles and Procedure

Polymerase chain reaction (PCR) is a technique that allows the generation of large amounts of a single DNA sequence from a mixture of sequences; the fragment generated can be designed to contain specific starting and ending positions based on the needs of the experiment. PCR is used to amplify specific regions of a DNA strand (the DNA target). This can be a single gene, a part of a gene, or a non-coding sequence. Most PCR methods typically amplify DNA fragments of up to 10 kilo base pairs (kb), although some techniques allow for amplification of fragments up to 40 kb in size.

A basic PCR set up requires several components and reagents. These components include:

Principle

Apart from PCR for generating large amounts of DNA, the second method is to use bacteria to replicate the DNA and then purify the replicated DNA from the bacteria. Plasmid DNA is usually the DNA of interest for this method. A plasmid is a double stranded circular DNA molecule that will replicate in an organism. A typical plasmid contains four important features:

The plasmid must be circular, because bacteria generally will not replicate linear ? DNA.

The plasmid must contain a sequence that functions as an origin of replication (ori).

The plasmid must contain a selection mechanism that will force the bacteria to retain the DNA; the most common type of selection mechanism used in bacteria is a gene for resistance to an antibiotic such as ampicillin or tetracycline.

The plasmid must contain a region for the insertion of the experimental DNA. A generic plasmid exhibiting these features is shown at right.

An expression plasmid that allows expression of foreign DNA should have a strong promoter segment for transcription of inserted DNA.

Must have an effective ribosome binding site that will allow efficient translation of the transcribed RNA.

Must have high copy number, i.e., the host bacterium should have many copies (usually >100)

Isolation of plasmid DNA from E. coli is a common routine in research laboratories. One can perform a widely-practiced procedure that involves alkaline lysis of cells. This protocol often referred to as a plasmid “mini-prep,” yields fairly clean DNA quickly and easily.

Procedure

Fill a microcentrifuge tube with saturated bacterial culture grown in LB broth + antibiotic. Spin tube in microcentrifuge for 1 minute, and make sure tubes are balanced in microcentrifuge. Dump supernatant and drain tube briefly on paper towel.

Repeat step 1 in the same tube, filling the tube again with more bacterial culture. The purpose of this step is to increase the starting volume of cells so that more plasmid DNA can be isolated per prep. Spin tube in microcentrifuge for 1 minute. Pour off supernatant and drain tube on paper towel.

Add 0.2 ml ice-cold Solution 1 to cell pellet and resuspend cells as much as possible using disposable transfer pipet.

Principle

The principle is to extract plasmid DNA from bacterial cell suspensions and is based on the alkaline lysis procedure developed by Birnboim and Doly (Nucleic Acids Research 7:1513, 1979). It is a known fact that plasmids are much smaller super coiled DNA molecules than the much larger and less super coiled bacterial chromosomal DNA. This difference in topology enables selective precipitation of the chromosomal DNA and cellular proteins and separates them from plasmids and RNA molecules. The cells are lysed under alkaline conditions, which denature both nucleic acids and proteins, and when the solution is neutralized by the addition of Potassium Acetate, chromosomal DNA and proteins precipitate because it is impossible for them to renature correctly (they are so large). Plasmids renature correctly and stay in solution, effectively separating them from chromosomal DNA and proteins.

Solution Preparation

1. Glycerol mix (1 L)

Weigh 25 grams (liquid weight) of glycerol and

Add dH₂O to 1 Liter (Autoclave).

2. Potassium mix (1 L)

170 mL of 1M KH₂PO₄ (monobasic),

720 mL of 1M K₂HPO₄ (dibasic), and

110 mL of dH₂O (Autoclave)

Preparation of Solutions

GTE buffer

50 mM Glucose,

25 mM Tris-Cl,

10 mM EDTA,

pH 8

NaOH/SDS lysis solution

0.2 M NaOH,

1% SDS

Transfer 1.5 mL overnight culture to a 1.5 mL microfuge tube, centrifuge for 30 sec, and decant supernatant.

Resuspend cells in 400 µL TE by vortexing, add 50 µL 10% SDS, 50 µL proteinase K (20 mg/mL in TE). Incubate for 1 hour at 37^oC.

Shear DNA by 3-5 passages through a 26 G needle.
Extract twice with 500 µL phenol: chloroform (1:1), and twice with 500 µL chloroform. 
Precipitate nucleic acids by adding 25 µL 5 M NaCl and 1 mL 95% EtOH, vortex, and centrifuge for 10 min, decant supernatant. Dry pellet.

Reagents

EDTA

Ethanol, absolute

Isopropanol

Phosphate Buffered Saline (PBS), 1X

Proteinase K

Sodium Acetate, 3 M pH 5.2 (Molecular Biology Grade)

Sodium chloride (NaCl)

Sodium Dodecyl Sulfate (SDS ), 10%

Tris EDTA (TE), pH 7.4

Tris EDTA (TE), pH 8.0

Tris HCl, pH 8.0

Reagents

Chloroform

EDTA, 0.5 M

Ethanol, absolute

Isoamyl alcohol

Phenol

Phosphate Buffered Saline (PBS), 1X

Proteinase K

RNAse A

Sodium dodecyl sulfate (SDS) solution, 10%

Reagents

Chloroform

EDTA, 0.5 M

Ethanol, absolute

Is amyl alcohol

Phenol

Proteinase K

RNase A

Sodium acetate, pH 5.2

Sodium chloride, 5 M
Sodium thiocyanate (NaSCN), 1 M

TE Buffer (Tris-EDTA), pH 7.4

Tween 20

Xylene

Principle

Restriction digestion is one of the most common reactions performed in molecular biology. Restriction endonucleases (RE) are also known as restriction enzymes, which recognize short, specific DNA sequences. There are three types of RE: Type-I, Type-II and Type-III. Type II RE, most commonly used for DNA analysis and genetic engineering, cleave double-stranded DNA (dsDNA) at specific sites within or adjacent to their recognition sequences. All Type II RE recognises a unique nucleotide sequence at which it cuts a DNA molecule and nowhere else. The recognition sequence is often a six base pair palindromic sequence (the top DNA strand from 5' to 3' is the same as the bottom DNA strand from 5' to 3'), but others recognize four or even eight base pair sequences. Many RE will not cut DNA that is methylated on one or both strands of the recognition site, although some require substrate methylation.

REs can also differ in the way they cut the DNA molecule. Some enzymes cut in the middle of the recognition sequence, resulting in a flush or “blunt end”. Other enzymes cleave in a staggered fashion, resulting in DNA products that have short single-stranded overhangs (usually two or four nucleotides) at each end. These are often called “cohesive ends”, as these single-stranded overhangs could potentially come together again through complementary base-pairing, as shown below:

Principle

Since the entire DNA sequence of the bacteriophage is known, we know exactly where a restriction enzyme will cleave the viral DNA and the size of the DNA fragments generated. This restriction enzyme digest will create a pattern of specific DNA fragments that will serves as a “DNA ladder”.

Reagents

Nuclease-Free Water: 14µl

10X Restriction Buffer: 2µl

Acetylated BSA (1mg/ml): 2µl

DNA (~1µg): 1µl

Restriction Enzyme (10u): 1µl

Final Volume: 20µl

Reagents

Restriction enzymes of choice, such as BamH1 and EcoRI

Restriction enzyme reaction buffer,

70 % Ethanol

100 % Ethanol

3 M Sodium acetate (pH 5.2)

Distilled water

Plasmid DNA isolated from bacteria, such as pGFP(R) and pBC(R)

Principle of DNA Ligase Mechanism

The process of connecting two pieces of DNA together is called ligation, and is catalyzed by an enzyme called ligase. The ligase used most often in molecular biology is derived from the T4 bacteriophage, and uses ATP to supply the energy necessary for the reaction. In addition to ATP, T4 ligase requires DNA with a 5´-phosphate group and free 3´-hydroxyl groups.

Applications

Ligation of blunt or cohesive-ended DNA fragments.

Repair of nicks in double-stranded nucleic acids.

Start with a 1:2 molar ratio of vector: insert DNA when cloning a fragment into a plasmid vector. This ratio will vary with other types of vectors, for example, cDNA and genomic cloning vectors. The following example illustrates the conversion of molar ratios to mass ratios for a 3.0kb plasmid and a 0.5kb insert DNA fragment.

Principle

The rate of joining of DNA fragments is affected by seven parameters:

DNA concentration,

Concentration of compatible ends,

Size of the fragments,

Presence or absence of complementary, single-stranded ends (some nucleases form blunt ends and in these cases special techniques are needed for joining),

G + C content and length of the complementary single strands,

Temperature of the reaction and

Ionic composition of the solution.

Principle

Plasmids requires hosts to replicate, hence it has to be inserted into bacteria. But efficiency of uptake of plasmid DNA by bacteria is low and will not do so without getting degraded. Therefore, to enhance the probability of uptake of the plasmid DNA by bacteria it is necessary to make the bacterial cells “competent” to absorb the plasmid DNA. One of the methods to increase efficiency of cell competence is given below. It should be noted that competent cells are more fragile than normal bacteria. Vortexing the cells, heating the cells above 42ºC or to 42°C for prolonged periods, or exposure of the cells to abusive treatments may kill them

Steps for Cloning

Prepare DNA.

Select restriction enzymes for your insert and vector, and determine the appropriate reaction buffers.

Combine the following in a microfuge tube (30 µL total volume):
2 µg DNA
1 µL Each Restriction Enzyme
3 µL 10x Buffer
3 µL 10x BSA
x µL H₂O (to bring total volume to 30 µL)

Transformation

The uptake of DNA by competent cells is called transformation. Transformation involves:

Mix a small volume of DNA (usually 1-3 µl) with 100 µl of competent cells.

The mixture is incubated on ice for 30 minutes to allow the cells to take up the DNA.

The cells are then heat-shocked at 37 to 42°C for 1 minute, and cold shocked on ice for 2 minutes.

The heat shock/cold shock reverses the effect of the competent cell process, by healing the damage inflicted by the competent cell solution.

Add 0.5 ml of LB culture mediumz

Incubate the cells for 10 - 30 minutes at 37°C to aid the healing process.

This cell/medium mixture is then spread onto bacterial culture plates containing agar, LB, and a selection mechanism.

Principle

Cloning experiments would be very difficult if we do not screen those very few cells that took up the recombinant plasmid DNA, as the transformation efficiency is very low as stated before (usually less than 1 in 10⁵ cells). Hence it is necessary that there should be a selection mechanism (i.e. conditions where cells grow if they express a gene, but die if they do not) to sort out which are transformed cells and which are not make the job easy.

A commonly used selection mechanism is antibiotic resistance. If the E. coli strain used is not resistant to the antibiotic, but the plasmid DNA contains a gene coding for resistance, then only the cells that have taken up the plasmid will be able to grow. Most commonly used plasmids contain a gene for resistance to ampicillin; only cells that have taken up the plasmid will be able to grow and form colonies.

Note: Uptake of plasmid DNA is rare; hence each group of cells visible on a plate represents the offspring of a single cell that will contain a single molecule of plasmid DNA.

Principle

The principle of Electrophoresis involves the motion of a particle in a fluid medium, where the gravitational attraction (on a flowing liquid) is the sedimenting force, and the frictional force is the opposing force and is proportional to the velocity of the particle. These forces balance each other acting in opposite directions and hence balance each other. This will lead to the uniform motion of the particle in the mobile liquid medium (i.e. the particle moves at constant velocity). In case the external field is an electric field instead of a gravitational field, a macromolecule will respond to the external field in two ways. In case the molecule is charged, it will migrate in an electric field to the electrode of opposite charge. Under this principle the technique of electrophoresis functions.

All electrophoresis operations are governed by the principle:

Agarose gel electrophoresis is the easiest and commonest way of separating, capable of resolving mixtures of DNA fragment that cannot be separated conveniently by other procedures. The purpose of the gel might be to look at the DNA, to quantify it or to isolate a particular band. The DNA is visualised in the gel by addition of ethidium bromide. This binds strongly to DNA by intercalating between the bases and is fluorescent meaning that it absorbs invisible UV light and transmits the energy as visible orange light.

Agarose, which is extracted from seaweed, is a linear polymer whose basic structure is shown in figure.

here are many methods for extracting DNA from gel apart from using commercial kits, some methods however yield cleaner DNA than others.

1. Freeze squeeze

Excise band and place pieces of it in a home-made spin-column (a piece of filter placed in a PCR 0.5ml eppendorf, pierced the bottom of the PCR tube with a needle). Place the PCR tube at -20 °C for 15-20 mins or freeze in liquid N2. Then place the PCR tube into the 1.5 ml eppendorf and spin at top speed in a microfuge for 15 mins, collect DNA solution which can be EtOH ppt or use directly.

2. Powdered silica

Melt excised bands at 70°C cool and add equal volume of TE-buffered phenol and mix. Spin for 5 min, remove aqueous phase, repeat and EtOh ppt. the DNA.

3. Electroelution