Under the influential leadership of Delbruck, who had a brilliant mind and charismatic personality, the phage group grew at tremendous pace. Besides Delbruck's own personal influence the reasons for this growth were:-

Under the influential leadership of Delbruck, who had a brilliant mind and charismatic personality, the phage group grew at tremendous pace. Besides Delbruck's own personal influence the reasons for this growth were:-

* The methods introduced by Dlebruck were extremely elegant. By using simple statistical tests he could answer many complicated questions.

* Techniques and concepts used by Delbruck and his groups had their origin in physics and this fact accorded these techniques a special prestige.

* The founding members of the phage group demonstrated that a revolutionary approach to biology was possible.

* The group had a specific target, to understand the process of self-replication, the key characteristic of life. Gradually it emerged that it was the same principle, that should explain the functioning and reproduction of all organisms from virus to mankind.

* The annual Cold Spring Harbor practical course on bacteriophage started in 1945 helped to create an informal network centred on Delbruck and the other founding members of the phage group.

The work of Francois Jacob (1920- ), Andre Michael Lwoff (1902-94) and Jacques Lucien Monod (1910-76), who initially formed the so-called the French School, played an important role in the growth of molecular biology. Monod started his research career at the Sorbonne, to understand the nutritive requirements of micro-organism. He learned about genetics at Morgan's laboratory in the USA, which he visited in 1936. In 1958 Monod and Jacob started their collaborative work on the regulation of enzyme synthesis in mutant bacteria. This work led to a greatly enhanced understanding of gene activity. In 1960 they coined the term 'operon' to represent a closely linked group of genes, each of which regulates a different step in a biochemical pathway. Then in 1961 they postulated the existence of messenger RNA that carried the required information for protein synthesis from the operson to the ribosomes, where protein synthesis took place. Lwoff worked in bacterial genetics. Jacob, Monod and Lwoff were awarded the 1965 Nobel Prize for physiology or Medicine.

Many of the techniques used in molecular biology are old techniques developed in other disciplines. Bacteriological techniques developed towards the end of the nineteenth century by the research schools established by Louis Pasteur (1822-95) and Robert Koch (1843-1910) respectively are widely used in molecular biology. These techniques were adopted and improved by the phage group.

The adoption of a molecular vision of biology was possible for the techniques developed for separating biological macromolecules and their constituents. These techniques were continuously improved throughout the twentieth century, often improvements accompanied by theoretical advances. In the first half of the 20th century the most widely used method for separating protein molecules was salt precipitation method. It was gradually replaced by chromatography. Various chromatographic techniques were developed or adopted for the separation of biological macromolecules_partition chromatography, ion exchange chromatography, affinity chromatography and so on.

But the techniques which really became the most powerful techniques for purification and characterisation of biological molecules were ultra-centrifugation and electrophoresis. These had tremendous impact on the development of molecular biology. The Rockefeller Foundation played a very significant role in the development and diffusion of these technologies. Theodore Svedberg (1864-1971) played a pioneering role in the development of analytical ultracentrifugation. The first ultra centrifuge was developed in 1924. Jesse W. Beams and Edward G. Pickels of the University of Virginia modified the ultracentrifugation techniques to make it more reliable and easy to use. The development of electrophoresis as a tool for characterising and purifying biological molecules was also initiated by Svedberg. However, its development was accomplished by Svedberg's student Arne Wilhelm Kaurin Tiselius (1902-71) who was awarded Nobel Prize in 1948 for the development of the electrophoresis apparatus. The electrophoresis apparatus initially developed was not only expensive but it was also very complicated to handle. By 1939 only 14 electrophoresis machines were in use in the USA. The electrophoresis machines were first commercially made by an American company called Klen. Then the development was fast. By 1950 four different companies were making electrophoresis apparatus. In the early 1950s optical observations were replaced by easily detectable labeled molecules and this tremendously enhanced the utility of the electrophoresis technique. Among the other techniques employed in molecular biology for characterisation were electron-microsope and x-ray diffraction.

The use of radio isotopes or heavier isotopes to 'label' molecules to follow their fate under physiological condition was employed in molecular biology. Compounds labeled with radioactive isotopes or heavier isotopes behave chemically like normal molecules but they can be detected by measuring their physical properties_the radioactivity or the mass. It was George Charles Von Hevesy (1885-1966) who first used radioisotope in 1923 to measure the uptake of a lead isotope by plant roots. Deuterium, a heavy isotope of hydrogen was discovered by Harold Clayton Urey (1893-1981) and this led to the use of deuterium labeled compounds and this also brought in use of mass spectrometers.

By the end of the nineteenth century most of the scientists accepted the Darwin's theory of evolution. But there were a few who disagreed with it claiming that it did not explain how changes originated in plants or how characteristics passed from one generation to the next. studies aiming to answer these question led the foundation of genetics. Gregor Johann Mendel (1822-84), who studied at Olmutz University before entering the Augstinian monastery at Brunn (now Brno in Czech Republic) in 1943, bred pea plants to find out how plants pass on particular features such as height and shape to their offsprings. Mendel noticed that characteristics like shape of their flowers were passed on to the next generation. He also observed that some features were more likely to be inherited than others. Mendel suggested that each characteristic was controlled by a pair of units (now called genes), one from each parent. Mendel's discovereis revealed the secret of heredity and formed the basis of modern studies in genetics. Unfortunately though Mendel published his work in 1866, its true significance remained unrecognised for more than thirty years.

In 1869 Johann Friedrich Miescher (1844-1895) had indicated the presence of nucleic acid in cell nuclei. Chromosomes, the thread like structures in cell nucleus, were discovered by Walther Flemming (1843-1905) in the 1860s by making use of the newly seynthesised aniline dyes. This new staining technique enabled flemming to follow in far greater detail the process of cell division which he called 'mitosis' from the Greek for thread. It is important to note that flemming detailed the fundamental process of mitosis _ the separation of the chromosomes along their lengths into two identical halves. He published his findings in his book, cytoplasm, Nucleus and cell Division (1882). However, it took another 20 years to realise the true significance of Flemming's work. The term 'chromosome' was coined by Wilhelm Waldeyer-Hartz or Heinrich von Waldeyer (1839-1921). It was also Waldeyer-Hartz who coined the term 'neuron'.

At the beginning of the 20th century scientists rediscovered Gregor Johann Mendel's (1822-84) work in genetics and biologists started exploring the role of chromosomes in heredity. By 1911 Morgan and his research school at Columbia University demonstrated the fact that chromosomes carried the agents of heredity. Morgan was born in Kentucky, USA. He founded the Department of Biology at the California Institute of Technology. Though at the beginning Morgan was one of the fierest critics of Mendel's theory but later he became its strongest supporter. In 1908 Morgan began breeding experiment with fruit flies to see whether the kind of changes Mendel had noticed in plants can also take place fruit flies. Morgan and his team found that Mendel's observation were rapplicable in fruit flies and they also discovered that the units suggested by Mendel were indeed actual physical units, placed at definite positions along each chromosome. They also succeeded in working at the first 'chromosome map'. This showed the position of genes on a chromosome.

In 1909 Phoebus Aaron Theodor Levene (1869-1940) found that nucleic acids contain aa pentose sugar, ribose and then 20 years later he found that there was another type of nucleic acid which contained different pentose sugar, deoxyribose i.e. a pentose sugar that lacks one oxygen atom. Thus it was established that there were two types of nucleic acids, ribonucleic acid (RNA) and deoxyriboncleic acid (DNA). Levene suggested a simple tetranucleotide structure for DNA and RNA (a nucleotide is simply one of the four bases plus a sugar and a phosphate). Though Levene established the molecular existence of nucleic acid independently of the protein but then their structure proposed by him was not only absurdly simple but also monotonous and repetitive and this was the reason why a generation of biochemists mistakenly sought for the strucutre of gene among the inexhoustible potential for the amino acids.

In 1928, Fred Griffith (1881-1941), the British microbiologist, demonstrated that when a mouse was simultaneously injected with nonvirulent R (rough) pneumococci of serological type-I and a heat-killed virulent form, S (smooth) pneumococci of type III the mouse succumbed to infection and eventually it died. Griffith was able to recover the virulent S pneumococci from the blood of the dead mouse. When either were inoculated separately no infection resulted. The obvious conclusion was that the virulent form though dead had transformed the nonpathogenic live type. Subsequently some other scientists reproduced Griffith's experiment in vivo and then J.Lionel Alloway demonstrated that transformation could be achieved in vitro.

This prompted scientists to study the transformation factor that is something in the dead form of pneumococci which was responsible for the transformation. In 1935 Oswald Theodore Avery (1877-1955), Colin MacLeod and Maclyn McCarty started a serious attempt to purify the transforming factor. Finally in 1944 they published their findings in the Journal of Experimental Medicine. Avery and his colleagues were able to show that the purified transforming factor had a high molecular weight, and was probably a nucleic acid. While Avery's paper did not have significant impact but it undermined the belief held by many biochemists and geneticists that genes were proteins. Though Avery could not conclusively demonstrate that the genes were made of DNA but then his experiments opened up a new line of inquiry.

Alfred Day Hershey (1908- ) and Martha Chase in their 1952 paper, Independent functions of Viral proteins and Nucleic Acid in Growth of Bacteriophage, demonstrated that the part of a bacteriophage responsible for its replication was its DNA and not proteins. The function of the protein shell of the bacteriophage was only to protect the phage DNA and act as syringe when a bacteriophage enters a bacterium. The Hershey -Chase experiment was one of the first experiments in molecular biology to use radiactively labeled moelcule. The earliest descriptions of the origins and development of molecular biology gave the entire credit to Hershey and Chase for the discovery of DNA's genetic role. But then Avery's experiment conducted eight years back which showed that the purified transforming factor had a high molecular weight and was probably a nucleic acid was given due credit. By 1952 the scientists were convinced on the following :

* Life-forms for their reproduction and growth use two categories of molecules_one category to store information and the other category act based on this information.

* DNA is repository of the genetic information and it is the enzymes or proteins which carry out the instructions.

* At the time reproduction the information is passed on in a nearly exact duplicate to the next generation.

What scientists did not know was what kind structure of DNA enabled all this to take place.

It were James Dewey Watson (1928- ) and Francis Henry Compton Crick (1916- ), working at the Cevendish Laboratory, who found out the structure of the DNA. In 1953 they published their double helical model. Their discovery is among few discoveries in science which had both immediate and far reaching implications. Officially they were not supposed to work on the structure of DNA. The official work on the structure of DNA was going on in the laboratory of Maurice Hugh Frederick Wilkins (1916- ) who had began studying DNA molecules by optical measurement. Wilkins observed that the DNA molecules would be ideal material for x-ray diffraction.

Watson was Salvador Luria's first doctoral student. For his PhD he had studied the effect of X-rays on the development of bacteriophage. However, interpretation of the data proved to be difficult. Watson at the instance of Luria went to Herman Kalckar's laboratory at Copenhagen. Under Kalckar's guidance Watson did not do any significant research. But after listening to a Wilkins's talk on the diffraction of X-rays by DNA fibres, which he happened to attend by chance, Watson decided to work in a crystallography laboratory. He joined the team headed by Max Ferdinand Perutz (1914- ) at the Cavendish Laboratory. At the time John Kendrew (1917-97) was also working with Perutz, both of whom received the 1962 Nobel Prize for Chemistry for their studies of the strcuture of globular proteins. Watson's official project was to purify and crystallise myoglobin, a protein analogous to haemoglobin but simpler in structure, a project which he never finished.

Crick, a physicist by training, began his research career under E.N. Andrade at the University College, London, where he worked on the measurement of viscosity of water. During the outbreak of the second world war he had to join the army and he worked on the design of acoustic and magnetic mines. At the end of the war Crick had no definite plan for his future career. He was contemplating to pursue research in pure science. Finally after going through Schrodinger's book, What is Life!, Crick decided to work on "major mystery _ the mystery of life and the mystery of consciousness". Thus in 1947 he began his work at the Strangeways Laboratory, Cambridge, on tissue culture. Two years later he moved to the Cavendish Laboratory to work on the structure of protein by X-ray diffraction analysis. And it is here he met Watson. Watson and Crick made an informal team to find out how the component atoms of DNA were arranged to give a regular structure to the molecule and make it chemically stable and at the same time enabled it to copy it faithfully.

Before Watson and Crick came into the scene much was already known about chemical and physical nature of DNA from the studies done by scientists like Phoebus Levene, Erwin Chargaff (1905- ), Alexander Robertus Todd (1907-97), and Linus Pauling. It was known that DNA consisted of a long chain of nucleotides. The DNA chain contained alternating sugar and phosphate groups. A nitrogenous base is extended off each sugar. DNA contains four types of bases adenine, guanine, thymine and cytosine. It was also known that DNA molecule was constant in width throughout its entire length. Using the existing knowledge and X-ray diffraction data of Maurice Hugh Frederick Wilkins (1916- ) and Rosalind Franklin (1920-58), Crick and Watson worked out the double helical structure of the DNA, which consisted of two helixes wound around each others, something like a spiral staircase. The steps of the stairs were made of paired chemical groups of atoms. The nitrogen bases turned inward from two parallel helixes paired with each others. It should be emphasised that the work of Wilkins and Franklin played a crucial role in the eventual discovery of the structure of DNA. In 1962 Crick, Watson and Wilkins were awarded the Nobel Prize for physiology or Medicine. Had Franklin not died very young from cancer she would have shared the prize with them. Nobel Prize is not awarded posthumously.

The model proposed by Watson and Crick also predicted a mechanism by which genetic information could be duplicated faithfully. The model also offered the key to understanding how genetic information could be stored in DNA. During replication the two strands of the double helix would separate before the chromosomes split leaving the nitrogen bases free to pair up again. Thus each strand acting as template for the other would build up its complementary strand on itself. The matching of the nitrogen on bases would ensure the accurate replication of the DNA molecule. By 1958 Matthew Stanley Messelson (1930- ) and Franklin William Stahl (1910 - ) showed that DNA does in fact replicate itself by separating the two strands, which serve as templates for creating the complementary sister strand. Their experiment is one of the classic experiments of molecular biology.

By 1956 George Emil Palade had shown a group of spherical bodies in the cytoplasm rich in RNA. These bodies called ribosomes soon found to be the sites of protein synthesis or information exchange. But then how does the information travel from DNA residing in the nucleus to ribosome in the cytoplasm, Mahlon Bush Hoagland (1921- ) discovered several different types of RNA molecules in the cytoplasm. These RNA molecules were relatively smaller and Hoagland called them transfer RNAs. Each type of transfer RNA was found to be capable of combining not only with a particular type of amino acid but also with a particular spot on ribosome. So a transfer RNA hooking to both amino acid and ribosome passed the information from the ribosomes to the proteins. The discovery of transfer RNA solved the problem of how the information passes from ribosome to proteins. But then at the first place who gave the information to ribosome.

In 1937 Crick in his lecture entitled "On Protein Synthesis" delivered under the aegis of the British Society of Experimental Biology presented a holistic picture of the principles of molecular biology. In a sense he set out the "philosophy" of the new discipline : "all the information required to create organisms can be found in molecules of DNA". In this lecture Crick stated that it was the sequence of bases which determined the specificity of nucleic acid which in turn determined the sequence of amino acids in proteins. It is in this lecture Crick postulated the so-called `central dogma' of molecular biology-information flows from a nucleic acid to a nucleic acid and then from a nucleic acid to a protein but the reverse is not true that is no information passes from protein to nucleic acid.

The relation between DNA and RNA was revealed by Monod and Jacob. They proposed that the DNA molecule first transfers its information to an RNA, which then moved out of the nucleus to the ribosome in the cytoplasm to give the information to the transfer RNA which in turn passed on the information to the amino acids to synthesise the proteins.

The next problem was to break the genetic code. In 1955 Severo Ochoa (1905-93) found an enzyme that could catalyse the formation of RNA-like substances from individual nucleotide. Then Arthur Kornberg (1918- ) synthesised such an enzyme for the DNA. They shared the Nobel Prize for Physiology or Medicine in 1959. The chemical nature of the entire genetic code was revealed by the work of Marshall W. Nirenberg (1927 - ) and Har Gobind Khorana ( 1922- ). They were awarded Nobel Prize in physiology or Medicine in 1968 for their interpretation of the genetic code and its function in protein synthesis. In 1970 Khorana and his colleagues succeeded in syntheising the first wholly artificial geen and then in 1976. Khorana inserted an artificially synthesised gene in a bacterial cell and which functioned properly.

With the development of recombinant DNA technology the march from molecular biology to genetic engineer's started. The first draft fo Human Genome was announced in 2000.

Some important terminologies used in moleculer biology/genetic engineering

Amino acids are naturally occurring biological molecules that possess both carboxy ( -COOH) and an amino (-NH2) group attached to same carbon atom. called x-carbon atom. Among the amino acids there are 20, that are used as building blocks for making proteins.

Bacteria are a diverse group of micro-organisms. They are structurally simple single cells without a distinat nuclear membrane. They constitute one of the five kingdoms of living things_the prokaryotic organisms of the living world.

Bacteriophage , also known as phage, is a virus that infects bacterial cells. Each phage has a narrow host range. Normally one phage infects only one type of bacterium. Most of the phages once inside bacterium cell take control of its genetic machinery and quickly multiply leading to the destruction (lysis) of the cell. Such phages are known as virulent phages. But some phages may remain dormant in the host bacterium. Such phages are known as temperate phages. They may be triggered to be active by environmental factors.

Chromatography is a technique for analysis and separation of mixtures of gases, liquids or dissolved substances. There are many types of chromatography like adsorption chromatography, partition chromatography and ion exchange chromatography. all types of chromatography involve two distnict types of phases_the stationary phase and the moving phase. The seperation depends on the competion for molecules of sample between the moving phase and stationary phase.

Chromosomes are thread like bodies found in nucleus of plants and animals. They carry the genes that convey hereditary characteristics, and are constant in number for each species. In human, each body cell contains 46 chromosomes (22 matched pairs and one pair of sex chromosomes). When the nucleus is not dividing individual chromosomes cannot be identified with a light microscope. However, just before the nucleus divides in two, the chromosomes contract and, when stained can be clearly seen under a microscope.

Clone is a collection of genatically identical copies of a gene, cell or organism. Clone is also referred to a genetically engineered DNA sequences.

Co-enzyme is the nonprotein portion of an enzyme. it can function as an acceptor of electrons or functional groups. Co-enzymes usually participate in enzyme-substrate reaction by donating or accepting certain chemical groups.

DNA (deoxyribonucleic acid), the genetic material of most living organisms, is a major constituent of the chromosomes within the cell nucleus. It plays a central role in the determination of hereditary characteristics by controlling protein synthesis in cells. DNA is a nucleic acid. It is formed of two molecules of polynucleotides coiled around each other. The two polynucleotide chains are linked together by hydrogen bonds between specific complementary bases to form a spiral ladder-shaped molecule or double helix. The two strands of DNA are complementary to each other. One base in one strands is linked to a base on the other strand by two to three hydrogen bonds. An adenine base remains always apposite a thymine and guanine is always apposite a cytosine base. For this arrangement the base sequence of one strand enables to determine the base sequence of the other strand.

DNA Finger Printing is a technique used for identification purposes in forensic science, paternity disputes and in veterinary science. In this technique an individual's DNA is analysed to find out the pattern of repitition of particular short of nucleotide sequence, called variable number tendem repeats, in the entire genome. This pattern is supposed to be unique to the individual.

DNA replication The process whereby DNA makes exact copies of itself is known as DNA replication. It is controlled by an enzyme known as DNA polymerase. For replication first the complementary bases on the two strands of the parent DNA molecule are broken down and the two strands are separated. Once the two strands are separated, each strand acts a template for the synthesis of new complementary strand. During the replication process the DNA polymerases move down the single strands and while doing so they link free nucleotides to their complementary bases on the templates. The movement of the DNA polymerases continue till all the nucleotides on the templates are joined with complementary free nucleotides. The end result of DNA replication is the formation of two identical strands of DNA. This process of replication is also known as semi-conservative replication because each new DNA molecule contains half of the original parent DNA molecule.

DNA sequencing (or gene sequencing) is the process of the nucleotide sequence of DNA. There are two methods of doing it _ the Maxum-Gilbert method and the Sanger method. The Maxum-Gilbert method named after Allan Maxam and Walter Gilbert uses restriction enzyme to cleave the DNA and radioctive phosphate to label each of the fragments. The Sanger method named after Frederick Sanger involves synthesing a new DNA strand using as template single stranded DNA from the DNA (or gene) being sequenced. This method is also known as dideoxy method.

Electrophoresis is a technique for the analysis and seperation of macromolecules based on the movement of the charged mocromalecular particles in an electric field.

Enzymes are proteins that act as catalysts in biochemical reactions. Each enzyme is specific to a particular reaction or group of similar reactions.

Gene is the basic physical unit of inheritance. A gene occupies a specific position on a chromosome. It may be visualised as a sequence of nucleotides of DNA meant for a specific function like synthesis of a single polypeptide chain or of messager RNA molecules corresponding to a particular sequence of the genetic code. Each human chromosome contains about 10,000 genes.

Genetic code The sequence of nucleotides in a gene determines the order of amino acids in the corresponding protein. Each base triplet of DNA (codon) like AAA, GGG, or TTT (where A stands for a denine, G for guanine and T for thymine) has a specific meaning corresponding to a different amino acid. These correspondences are known as the genetic code. There are 64 possible codes from the combinations of the four bases present in DNA and messenger RNA. Some amino acids may have more than one codon and some codons do not correspond any amino acids but have other function.

Genome refers to all genes in a complete set of chromosome of an organism of a particular species.

Human Genome project is an international research effort began in 1980s to map and sequence all genes found in human genome.

Messenger RNA or mRNA is responsible for carrying genetic code transaribed from DNA to ribosomes where protein synthesis takes place.

Mutation is an abrupt change in the genotype of an organism. It may make a living cell and all cells derived from it different in appearance or behaviour from the normal type. An organism affected by mutation particularly when its effect is expressed in the phenotype is known an mutant. Under natural condition the rate of mutation is very slow but this may be enhanced by radiation and by some chemical agents. In most cases mutation is harmful but in few cases they may be useful to an organism by increasing it fitness. So mutation is essential for evolution as the ultimate source of genetic variation.

Nucleotide is the structural unit of nucleic acids_DNA and RNA. A nucleotide has three parts - a phosphate group, a pentose sugar (ribose in case of RNA and deoxyribose in case of DNA) and a base. DNA contains four bases viz., adenine, thymine, guanine and cytosine. RNA also contains four bases but instead of cytosine it has uracil. In nucleic acids, which are polynucleotides, the nucleotides are linked together by covalent bonds between the sugar (of one nucleotide) and the phosphate (of the next nucleotide).

Polymerase chain reaction is a method of multiplying a fragment of DNA. It is used as an alternative to gene cloning as a means of amplifying genetic material.

Proteins are the most important components of organisms. They occur in all plants and animals and are essential to the diet of animals. Proteins act as enzymes _ the most effective catalysts for biochemical reactions. An enzyme may enhance the rate of reaction by ten billion times. They play structural role by contributing to the architecture of the cell. They can also bind to genes to control their activity. Protein molecules consist of one or several long chains of amino acids. Proteins are made up of 20 amino acids. The specificity of a protein is determined by the number and nature of the amino acids that it contains and by the sequence of the amino acids in which they are ordered.

Ribosome, a small spherical body within a living cell, is the site of protein synthesis. There are some ribosomes in a living cell. Ribosome consists of two subunits one large and one small. both the submits are comprised of ribosomal RNA and protein.

Retrovirus is a virus having RNA as the genetic material. Inside host cell the viral RNA is used as a template for making viral DNA which then get integrated into the host cell's chromosomal DNA.

Reverse transcriptase is an enzyme that uses RNA as a template for making DNA.

Recombinant DNA is the DNA made by joining DNA fragments from different sources using the techniques of genetic engineering rather than by breeding experiments.

Plasmid is small circular bacterial DNA that can exist and replicate independently of the chromosome. Plasmids are widely used as vectors to produce recombinant DNA for gene cloning. Plasmids are also occasionally found in certain fungi and plants.

Restriction enzymes are a type of enzymes that cut molecules of foreign DNA at particular site. Many bacteria produce such enzymes to protect them, because such enzyme destroy the DNA of invading virus buy cutting it into pices. These enzymes are widely used in genetic engineering.

RNA (ribonucleic acid) is a long chain of polynucleotides in which the sugar is ribose and the bases are adenine, cytosine, guanine and uracil. unlike DNA it is single stranded with helical regions formed by base pairing. In some viruses RNA is also the hereditary material.

Transfer RNA or tRNA is involved in the assembly of amino acids in a protein chain being synthesised at the site of protein synthesis.

Ultracentrifuge is a high speed electrically driven centifuge used for measuring the rate of sedimentation of colloid particles or for separating macromolecules such as protein or nucleic acids from solution.

Viruses are not independent organisms. A virus consists of a core nucleic acid (DNA or RNA) which is surrounded by a protein coat. They are parasites of animals, plants and some bacteria. A virus is too small to be seen with a light microscope and it cannot be trapped by filters. A virus in not capable of reproducing on its own. However, once a virus is inside its host cell, it hijacks the cell's machinery to express its genetic information.

Vector is a vehicle used in gene cloning to carry recombinant DNA into the genome of a host cell. For bacteria hosts three different types of vector are used _ bacteriophage, plasmid and cosmid.

National Research Centre for Onion & garlic

Onion and garlic are important spice commodities consumed all over the world in various forms. Their use is not limited to any climate and is not associated with particular nationality. Onions are found in most markets of the world in all seasons of the year. They are consumed in about the same amount when the prices are high or low i.e., demand for these crops is fairly constant. In India, no culinary preparation is complete without onion and garlic.

Onion and garlic have been in use since time immemorial. One of the most important testimonials to the use of onion as food in ancient Egypt is from the Bible. According to Tackholm and Drar, onion and garlic has always been a popular food in Egypt. Horodotus (484B.C.) visited pyramids at Giza and found inscriptions on pyramids implying that builders used to consume reddish onion and garlic. In India onion was treated as "taboo" by the respectable people as recorded in "Apastamba Dharma Sutra-I" in the Sutra period (860-300B.C.). "Charaka Samhita" and "Susruta Samhita" throw some light on the medicinal value of these crops. Patanjali's "Mahabhashya" mentions the use of onions by non-vegetarians only. A Sanskrit equivalent called "Palaudu" has been recorded in "Rigveda " signifying its usage in Vedic India.

The latest global review of area and production shows that among the major vegetables, onion and garlic rank second and fifth in area, while third and seventh in production, respectively. About 40 million tonnes of onion and 11.7 million tonnes of garlic are produced from an area of 2.3 million and 1.3 million hectares, respectively. India ranks second by area next to China for both the crops (4.05 and 0.96 lakh hectares, respectively). However, by production it ranks second for onion (43 lakh tons) and third for garlic (4.10 lakh tons) in the world.

Besides feeding huge domestic population, India exports 4.5 to 5.0 lakh tons of onion annually worth Rs. 250 to 300 crores. Onion export has increased three times over the decade. During last 10 years, the area, production and productivity of onion has increased by 34, 54 and 15 per cent respectively. Yet the productivity of onion (10.61 tons/ha) is very low as compared to USA (42.95), Netherlands (39.13) and China * (22.23). While in garlic (4.29 tons/ha) productivity is far low as compared to China (14.53) Korea rep. (11.25), Spain (7.5) and Brazil (5.16). Research on onion and garlic is going on in the country for the last four decades under Agricultural Universities and ICAR system. Prior to the Agricultural Universities, research on maintenance of land races and standardization of agro techniques was attempted by the State Agricultural Departments. With the concept of co-cordinated projects and Agricultural Universities, the work on onion and garlic research was strengthened. Nearly 33 varieties of onion and 11 varieties in garlic have been released by different oganizations.

Despite the release of a number of varieties in both the crops, the area coverage under released varieties is not more than 30 per cent. Local types and land still dominate the production. The local types suffer from many drawbacks viz., low yield, productivity and susceptibility to different insect pests and diseases. Besides, this the susceptibility to foliar diseases results in lowering of productivity. Commercial multiplication and distribution of seed of released varieties is very poor. The concept of crop planning is not followed as a result of which there is always an "on" and "off" year for onion. The exercises greatly influence on availability /arrivals of onion and thereby, fluctuation in prices. Further unstable export policy leads to chaos in the market. Because of tropical climate and inherent capacity of the genotypes, the storage losses are very high. All these problems needed a proper appraisal. Considering these issues, it was well thought of taking up strategic research on these commodities by ICAR. Hence, National Research Centre for Onion and Garlic was established in Sept. 1994 at Nasik. Thereafter it was shifted to Rajgurunagar (Pune) in 1998.

The institute collects, maintains and acts as national repository for onion and garlic germplasm. It is developing hybrids/varieties suitable for domestic as fighting fit as export market coupled with resistance to biotic and antiabiotic stresses. It also tries to enhance and sustain productivity and quantity of seed as well as bulb crop through agronomic manipulations. The institute is engaged in developing packages for post harvest handling and value addition. And it acts as clearning house of research and general information relating to onion and garlic. The Immediate tasks before the institute are, In Onion: Development of varieties/hybrids resistant to purple blotch, Stemphylium blight and basal rot. Development of yellow onion varieties/hybrids suitable for export with good storage characteristics. Development of male sterile lines along with short day adapted maintainer lines for exploitation of heterosis on commercial basis. Development of varieties/hybrids suitable for Rangda (Late Kharif) season. Use of biotechnological approach for resistance breeding and heterosis breeding. Standardization of fertigation techniques. Development of integrated pest management practices for reducing reliance on pesticides and fungicides. Standardization of post harvest techniques for reducing storage and transport losses. including a) improvement in storage structures b) Use of irradiation techniques on a commercial scale c) improvement in packing for the domestic as well as the overseas markets. In the Case of Garlic the immidiate tasks are: Development of big cloved garlic and more number of cloves per bulb. Creation of variability in garlic through conventional and non conventional tools. Development of varieties with early maturity. Virus free garlic through meristem culture. In-vitro conservation of garlic germplasm

Although onion is planted almost year round in most of onion areas, 60% produce comes from rabi crop, harvested in April-May. After proper curing the bulbs are stored in storage strcutures for about 4-6 months. Storage life of onion, besides genotypes and cultural practices, depend upon storage environment augmented by different storage structures.

Chinese garlic has made an official entry in Indian Market in 1999. Big cloved compact garlic bulbs weighing more than 30g became quite popular in Mumbai and Chennai market. About 40,000 tons of garlic was imported from China and Korea. This long day type garlic has high yield potential under low temperature and long day conditions. The traditional garlic growing areas of MP, Gujarat, Orissa and Maharashtra cannot grow these long day varieties due to climate barrier. Farmers from these areas will have to compete with long day types being imported in future by way of maintaining quality of their local material. Research will have to take a note of this and plan for development of big cloved garlic which can be grown under short day and short winter conditions of peninsular India.

Kharif onion is mostly grown in drought prone areas of Maharashtra, Karnataka, Andhra and Gujarat, which accounts for 20% of total production. There is demand for dark red bulbs with moderate keeping quality and tolerance to collectotrichum and purple blotch. The harvest should match with September - November arrivals in market. There is dearth of varieties which can match with above requirements. Earlier recommended varieties suffer from one or the other problems. The situation therefore demands for development fo varieties suitable for Kharif.

Degeneration of garlic due to latent virus diseases is very common. Healthy breeder stock can be produced through meristem-tip culture. Necessary facilities for tissue culture and other biotechnological studies are being developed.

Access to documented information is highly essential for planning reaserch programme. Internet, E-mail and Hort C.D. Rom facilities have been created for easy review of literature at the institute.

- Based on the information supplied by the National Research Centre for Onion & Garlic (NRCOG)

Recent Developments in Science & Technology

Solar Energy based space vehicle

A lots of money are required to launch each pound of payload into orbit, so space scientists are always trying to low down the costs. The latest idea is a vehicle, developed by Boeing, that could nearly double propulsion efficiency-saving costly propellant. The key is - solar power. Tom Kessler, program manager of Boeing's Phantom Works research and technology development group, says Solar Orbit Transfer vehicle, which is space craft from a low-Earth to upper stage orbit, works with very simple principle. In this space craft, engine works like a giant boiler and the sun is used as a main source for heating that boiler.

A 10-meter-wide parabolic mirror reflects sunlight to secondary concentrator, and magnifies fying solar energy upto 10,000 time, to temperatures around 3,5000F. The heat makes liquid hydrogen propellant flash to a gas, like water on a hot griddle. The hydrogen then exits through a rocket nozzle to thrust the vehicle forward.

This vehicle can also generate electric power for a spacecraft once it reaches its destination, adds kessler. Using this solar power up to 100 kilowatts can be generated . In a 48 million dollar Programe funded by U.S. Air force, Boeing plans to build a half size or smaller system to fly in 2004. Engineers have completed a series of all ground test. Source: Popular Science, Oct.-2000

Silk from Milk

People have known about the superior strength of silk at least since the days of Changhez Khan, whose warriors used to weave the material into their armour to stop arrows. Khan's silk made by silkworms, would be no match for modern bullets. But today's armies are looking to spider silk, the strongest material known for the next generation.

Unlike worms, spiders cannot be raised in large number because they are territorial. But scientists at Montreal-based Nexia Biotechnology realized that the spider's silk gland is anatomically similar to a goat's mammary gland.

When the spider gene is inserted into the mammary glands of live goats, the animals produce silk protein in their milk. The protein must be extracted from the milk and spun into a fibre, just as a spider spins a web.

Nexia already has a herd of more then 20 "Biosteel goats" each of which may produce as much silk as 10,000 spiders. The U.S. and Canadian armies are interested in using spider silk to make lighter, stronger bullet proof vests. A silk cable as thick as your thumb would be able to haul down a jet fighter.

Source: Popular Science, Oct.-2000

First Aid for Brain

In coming years, accident vectims may be screened for brain damage before leaving the scene,enabling rescuers to make vital treatment decisions that save time and lives. A new head-mounted device being developed at Oak Ridge National Laboratory uses low frequency sound waves that penetrate the skull to detect bleeding or swelling within the brain- technology similar to that used during prenatal ultrasound system.

The result, however, won't replace more detailed imaging technology such as CATscans. But they will be able to immediately identify abnormalities such as hemorrhages, clots, or tumors,allowing doctors to intervene before more permanent damage sets in. This test takes 1 to 2 minutes and its equipment is relatively inexpensive.

Source : Popular Science, March-2000

Smoke -Eating Device

A bottle size device could lead to less polluting, more fuel- efficient automobiles.The metal device, named as the plasmatron,was discovered in 1993 by MIT researcher Daniel Cohn and his colleagues. It was tested in a commercial car engine and the results are promising. It reduced nitrous oxide emission by between 80 and 90 percent.

Using an arc of electricity, Plasmatron converts about 25 percent of gasoline to hydrogen rich gas - a combination of pure hydrogen and carbon monoxide - before it enters engine's combustion chamber. This gas or plasma, allows the engine to run leaner that is, with more air and less fuel - and thus reduces emissions. Cohn also says this device will improve fuel efficiency by converting gasoline to plasma. Cohn sees applications beyond reducing the emission of today's car and trucks. "In the near future, the plasmatron could make hybrid vehicles nearly as clean as fuel cell vehicles" he says. and it could eventually help create onboard hydrogen for fuel cell vehicles.He adds that the device could also be used with diesel engine.

Source: Popular Science, March-2000

Earth- Quake Resistant Buildings

39 stories apartment building is under construction in San Francisco. which will be the tallest precast concrete structure ever built in an area of high seismic activity. Charles Pankow, Builders of Altadena, California, is using an innovative new construction that could revolutionize the way building are build in seismic zones.

Conventional cast in place and precast systems survive earthquakes by dissipating the energy through the structure, often doing irreparable damage to themselves in the process.This new technology developed with the help of the University of Washington and National Institute of Standards and Technology, consists of high strength steel reinforcing cables and mild steel bars that stretch slightly during an earthquake , then snap the building back into the place. The steel components also dissipate seismic energy before it can attack the structure. That means less damage to beams, walls and ceilings. The innovation will also save the money. Source: Popular Science, July-2000

Compiled by : Kapil K Tripathi