Daiamonds may soon be everyone's best friend. According to enthusiasts, synthetic diamonds have already or will soon appear on watch crystals, eyeglasses, optical instruments, audio speakers, fuel injection nozzles, turbine blades, scalpels, and semiconductor wafers, to name only a few applications. The remarkable properties of diamond were recognized long ago. The name originates from the Greek adamas, which means invincible. Diamonds, particularly large ones, are among the most desirable gemstones, but the scientific and industrial value of diamond films and small diamonds is perhaps even more striking. For hardness, for electrical resistance, for corrosion resistance, and for thermal conductivity, diamonds are at the extreme. Diamond also absorbs less light at most wavelengths, and also exhibits ten times greater thresholds to laser damage. Its thermal properties can be improved even further by making pure carbon-12 isotopic diamonds. Diamond circuits could be more stable and would remove accumulated heat more rapidly than the silicon wafers that are the current core of the semiconductor industry. Last year a new feature, the Molecule of the Year, was initiated by Science with the idea of honoring the scientific development of the year most likely to have a major impact on scientific advances and societal benefits [Science 246, 1541 (1989)]. The condition for selection was not that the development had to be discovered in the year of the choice, but rather that in that year the accumulation of experience and expertise indicated that the discovery was on a pathway of major importance. The polymerase chain reaction was picked as the Molecule of the Year for 1989, and the exponential increase in 1990 in its use in the laboratory, in industry, and in the courtroom supports that selection. Diamonds in 1990 seem to be at the equivalent stage. There are cost factors and theoretical problems to overcome, but the mounting excitement in conferences, journals, and industrial laboratories indicates that the threshold in the development of a new technology has been passed. A more detailed account of the diamond development. One of the intriguing aspects of the synthetic diamond technology is its relation to the discipline of materials science. That area of modem science, a child of physics, engineering, and chemistry, has flourished enormously in recent years, producing such practical applications as transistors, superconductors, and designer catalysts. Materials science has a history of symbiosis between academe and industry and is driven by the interplay between fundamental research and practical applications. Materials scientists constantly search for new phenomena and new combinations of existing properties. These discoveries can lead to previously unimaginable technologies or can decrease the cost of existing applications so that they become accessible to a wider range of problems. This is one of the reasons materials scientists are so excited about thin diamond films. They will now be able to exploit the incredible properties of diamond in situations that were discarded as impractical in the past. For example, electronic devices in which diamond forms the substrate, or backbone, for the device would be inconceivable without the ability to grow diamond as a film. Moreover, materials scientists are aware that knowledge diffuses like ions hopping in a lattice, so that other promising materials, such as boron nitrides, will benefit from the new science revealed by diamond studies. As we watch the sudden rise in expectations and knowledge of diamonds, do we need to fear side effects ofunknown consequence? No obvious difficulties are apparent, other than the economic readjustments usually accompanying any new technology. Electromagnetic radiation, antibiotics, and transistors are only a few of the scientific discoveries that have spawned new industries and enriched all our lives. That they have in turn created new societal problems should lead neither to cries of dismay nor shouts of alarm. Who really wants to get rid of television sets, life-saving drugs, or computers? Synthetic diamonds may well create new problems requiring new science and new ingenuity, but the potentialities for new frontiers more than outweigh the possible adversities. Scientists who say, 'The solution to problems created by science is more science," must expect to be viewed with a certain amount of skepticism by the general public. Scientists must therefore do their best to predict in advance that the mainline benefits are likely to outweigh the sideline problems, in which case the public will find that science, like diamonds, can be everybody's best friend. The Molecule of the Year Daniel E. Koshland Jr. Science, 250 (4988) 1990

In 1992, The Science Magazine declared "The Molecule of the Year" was nitric oxide, NO, a molecule of versatility and importance that has burst onto the scene in many guises. In the atmosphere it is a noxious chemical, but in the body in small controlled doses it is extraordinarily beneficial. It helps maintain blood pressure by dilating blood vessels, helps kill foreign invaders in the immune response, is a major biochemi-cal mediator of penile erections, and is probably a major biochemical component of long-term memory. These are just a few of its many roles, which are just beginning to be discovered, and they are discussed in the accompanying Molecule of the Year story (p. 1862). That NO plays so many roles is not surprising because the same biological second messengers usually are used in many diverse systems, but a gas was indeed a surprise for an endogenous role, and a labile and toxic gas even more so. As the first surprise of such an unlikely agent was overcome, the gas as a messenger seemed logical because it could pass through biological membranes readily and oxidize foreign substances. NO's role in sexual dysfunction, that of impotence, supports further a new liberation from old mental straitjackets. The future is sure to bring more insights into the effect on complex processes such as IQ, bad behavior, and alcoholism by single genes or chemical reactions. Many people will be happy to learn that some forms of sexual dysfunction may not be caused by psychiatric disorders or the failure of a marriage but may instead reflect a deficiency in a chemical reaction that can be compensated for by medical treatment. New research on the role of NO may also lead to new insights into the loss of memory, which is so debilitating to so many. This year's Molecule of the Year once again shows that scientific rewards can come from pursuing unconventional thinking. The recent presidential election focused on the persistent question of providing jobs and correcting ailing economies. Hopefully, the political and social scientists advising our leaders will pursue these problems with the same creativity that charac-terized the research on NO. The new, the unexpected, and the incongruous will be needed to address these social problems. In addition, our elected officials as well as the general public must face unpleasant realities, including the need for the United States to work hard to maintain its standard of living in a competitive world and the need to be open-minded enough to welcome unexpected solutions such as gaseous messengers. Every year Science picks a Molecule of the Year along the lines described in our editorial of 22 December 1989. Molecule is a term we use to emphasize that we are honoring the discovery rather than the people who made the discovery, not because people are unimportant but because many other awards honor the discoverers, and most discoveries involve the contributions of many people. As in the case of "people prizes," there are many "runner-up" discoveries that are extremely important to humanity but, in our opinion, are not yet quite as developed as our winner. For example, one of our runners-up, the discovery of the structure of nitrogenase, has no immediate industrial application, but the way enzymes fix nitrogen is bound to be of great importance to agriculture. As more intense farming and cheaper fuel become the necessities of the future, better mechanisms for nitrogen fixation become more important. Enzymes certainly appear to have solved the problem better than man-made solutions so far. The hope is that the enzyme mechanism and the chemical knowledge can be combined to make a new solution that will benefit millions. The widespread use of super-computers is not a sudden event, but the increased utility of this powerful tool in industry and science for applications such as aircraft design and oil exploration will solve many problems that were previously beyond approach. All of the runners-up are discussed in the accompanying story. This year they are an impressive group ranging from discoveries that are already being applied, such as fetal diagnosis and treatment (in utero treatment of a fetus to correct its deficiencies and transplanting fetal tissue to adults with Parkinson's disease), to those that are now far enough along so that application seems inevitable, for example, antisense RNA. In addition, there are landmarks such as the mapping of chromosomes Y and 21, which will certainly lead to medical discoveries, and the use of magnetic resonance imaging to diagnose medical problems and to locate areas of the brain identified with specific thought processes. Those who sometimes question the advances of science should think for a moment about the incredible developments that have slipped into everyday life without headlines. The Molecule of the Year and the runners-up are a good place to start for the discoveries that will inevitably make the future better than the past. Daniel E. Koshland, Jr. Science Magazine, 1992

Targeting a gene for epigenetic modification by a transcription factor. In some cases, transcription factors may bind to a specific gene and initiate a series of events that leads to an epigenetic modification. For example, particular transcription factors in stem cells initiate epigenetic modifications that cause the cells to follow a specific pathway of development. For this to occur, the transcription factors recognize specific sites in the genome and recruit proteins to those sites, such as histone-modifying enzymes and DNA methyltransferase. This recruitment leads to epigenetic changes, such as changes in chromatin structure and DNA methylation. Please go through the diagram for the illustration.

Systematically Onychophora presents a unique position: • The characters of Onychophora have made it most interesting from the point of view of evolution. It is an oldest terrestrial group which probably originated from some marine ancestors. • It has attained a number of features for terrestrial life, i.e., internal fertilization, viviparity, semi-solid excretory product, less permeable skin, etc. But at the same time the structure of spiracles speaks about its limitation on land life and thus shows its primitiveness. • The resemblances with annelids are probably the examples of convergence. Onychophorans have a mixture of morphological characteristic features which make them effectively cross between the Annelid worms and the Arthropods. But our modern understandings suggest they do not represent a missing link between the annelids and the arthropods. • Presence of variously developed specialized characters in Onychophora, such as trachaea with open spiracles and the origin of jaws do not support the above view that Onychophores represent a missing link. Instead, like the Tardigrades they are considered as a separate line of evolution and arose independently from some forgotten ancestor. • Again the common characteristic features of Onychophora regard a common relative to annelids and arthropods. Hence, it is regarded as a living connecting link between two phyla and it is undoubtedly an ancient form but not an ancestor of arthropods. • Kaestner (1967) has stated that the Onychophora probably represents an early lateral branch of the evolutionary line terminating in the arthropods. Peripatus are also called living fossils because they truly represent archaic animals and have changed little in their body shape for about 500 million of years. • A cladistic analysis which places the Onychophora in an intermediate position between the Polychaeta and the Tardigra-Arthropoda clade. The current view is that the Onychophora represent a sister group to the Arthropods on the basis of morphological, palaeontological and molecular data. • According to Marshall and Williams (1972)-Onychophora can be rightly described as an aberrant arthropods or highly modified annelids and can be placed all the species under twelve genera of Onychophora in a separate subphylum “Onychophora” under the phylum Arthropoda. But absence of jointed chitinons exoskeleton and jointed segmental appendages do not support the inclusion of Onychophora within Arthropoda. • Some peculiar features of Onychophores which support neither annelids nor arthropods, and demand a separate phylum status. Ruppert and Barnes (1994) pass the remark that Onychophorans are not usually considered arthropods rather a phylum animals closely related to arthropods.

The shorter and longer arms of a submetacentric chromosome are referred to as :- (1) s-arm and l-arm respectively (2) p-arm and q-arm respectively (3) q-arm and p-arm respectively (4) m-arm and n-arm respectively

Model Answer:

2. p and q are shorter and longer arms of a sub-metacentric chromosome. Submetacentric chromosomes have the centromere slightly offset from the center leading to a slight asymmetry in the length of the two sections. Human chromosomes 4 through 12 are submetacentric in nature.

Consider following features: (a) Organ system level of organisation (b) Bilateral symmetry (c) True coelomates with segmentation of body Select the correct option of animal groups which possess all the above characteristics. (1) Annelida, Arthropoda and Chordata (2) Annelida, Arthropoda and Mollusca (3) Arthropoda , Mollusca and Chordata (4) Annelida, Mollusca and Chordata

Model Answer:

1. True segmentation is seen in the Phylum Annelida and Chordata. Arthropods too show segmentation restricted to upper side of their body. In chordates, segmentation is pertaining to muscular part as it shows Circular & longitudinal muscle perpetuates throughout the body.

Which of the following statements is not correct? (1) Lysosomes have numerous hydrolytic enzymes. (2) The hydrolytic enzymes of lysosomes are active under acidic pH. (3) Lysosomes are membrane bound structures. (4) Lysosomes are formed by the process of packaging in the endoplasmic reticulum.

Model Answer:

4. Lysosomes are formed by the process of packaging in the ER

Which poriferan is commonly known as "Dead man's finger" Or "Mermaid's gloves" A. Hyalonema B. Chalina C. Clion D. Oscarella

Model Answer:

B. Chalina It resembles the fingers of a hand which has many oscula. Chalina belongs to the class of Demospongia and order Monaxonida

Predator-Prey relationship

Model Answer:

C

Which of the following factors is responsible for the formation of concentrated urine? (1) Low levels of antidiuretic hormone. (2) Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys. (3) Secretion of erythropoietin by juxtaglomerular complex. (4) Hydrostatic pressure during glomerular filtration

Model Answer:

Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys. Which involves Loop of Henele and vasa recta.