.... uses RNA templates to produce DNA. For example, within the core of HIV is a double molecule of ribonucleic acid, RNA. When the virus invades a cell, this genetic material is replicated in the form of DNA . But, in order to do so, HIV must first be able to produce a particular enzyme that can construct a DNA molecule using an RNA template. This enzyme, called RNA-directed DNA polymerase, is also referred to as reverse transcriptase because it reverses the normal cellular process of transcription. The DNA molecules produced by reverse transcription are then inserted into the genetic material of the host cell, where th .....

.... and gaudiest patterns. The moon seems to play an important role in fish reproduction. According to Peter H. Pressley, it appears that the moon/s light may be as important as its gravitational pull. "Some fishes may use periods of maximum moonlight for effective nest guarding during the week or so it takes for many demersal eggs to incubate. Since the larvae of many dermersal-spawning species are light sensitive, bright moonlight may help to orient them towards the water's shallows after nighttime hatching." (P 96) Regional weather patterns such as monsoons, periods of high wind velocity, and major current shifts affect procr .....

.... calculation. These early computers had no need for an operating system and were operated directly from the operator's console by a computer programmer, who had immediate knowledge of the computers design. By the early 1950's punched cards were introduced, allowing programs to be written and read directly from the card, instead of using plugboards. Second Generation Computers (1955-1965) In the mid-1950's, the transistor was introduced, creating a more reliable computer. Computers were used primarily for scientific and engineering calculations and were programmed mainly in FORTRAN and assembly language. As computer .....

.... contain the information of a person's potential height, potential strength against disease, and other physical characteristics. A human being has 23 pairs of chromosomes in every cell in his or her body (except reproductive cells). If, during a stage of growth, a fetus somehow loses one of these chromosomes, the baby may die, or have a birth defect. Since this error is written on their genes, they may pass it on to their children, who may or may not have anything wrong with them. The way a person looks, as I have stated, is hereditary. In humans, brown eyes are dominant. Thus, if a person with brown eyes and a reces .....

.... a carton. Think if you smoked two packs a day for 30 years, multiply that by the price of a pack a cigarettes (think about the fact that the price is almost certain to rise within that time), that’s a lot of money. Then you have the cleaning and air freshening bills about every 2 or 3 months. There would be cost to burns on your clothing and furniture. Smokers have become more and more unpopular in recent years due too the dangers of second hand smoke. Smoking not only affects you, but can also affect the people around you. New state laws and ordinances are even starting too prohibit smoking in public places. Therefor .....

.... melting of the polar icecaps and hence a major rise in sea level, along with other severe environmental disturbances. An example of a runaway greenhouse effect is Earth's near-twin planetary neighbor Venus. Because of Venus's thick CO2 atmosphere, the planet's cloud-covered surface is hot enough to melt lead. Water vapor is an important "greenhouse" gas. It is a major reason why humid regions experience less cooling at night than do dry regions,. However, variations in the atmosphere's CO2 content are what have played a major role in past climatic changes. In recent decades there has been a global increase in atmospheri .....

.... environmental impact while creating minimal economic distortions. For the purpose of this essay, pollution shall be identified as follows "...the deliberate or accidental introduction to the environment of contaminants, in the form of either wastes or products " (Bryner, 10). This essay will deal with the problem of air pollution. Air pollutants come from heavy industry, fumes from automobiles, jet planes and the like. When speaking of the automobile alone "...each gallon of gas burned releases 22 pounds of carbon dioxide in the atmosphere...the car is the single largest contributor to global warming " (Rifkin 179). A .....

.... more likely to have the disorder than girls. The symptoms of ADHD usually decrease with age, but those symptoms related with other similar disorders are said to increase with age. 30-50% of children with ADHD may display symptoms, although often times less severe, into adulthood. ADHD may be observed in children before the age of four, but it’s signs are often missed until the child begins school. ADHD is often accompanied by learning difficulties, excessive physical activity, impulsive actions, inattention and social inappropriateness. Many of the children affected by ADHD exhibit a low threshold for frustration .....

.... measure the height of all the plants at the end of six weeks and record the data. The first step of photosynthesis is the absorption of light by a chlorophyll molecule. "The energy of the absorbed photon is transferred from one chlorophyll molecule to another until it reaches a site called a reaction center....One oxygen molecule is produced per eight photons absorbed." (Alberty 708) James Huheey, professor at the University of Maryland, talks about chlorophyll in his book Inorganic Chemistry: "Chlorophyll absorbs low-energy light in the far red region....Such absorption serves a twofold function: (1)The energy may be passed alo .....

.... Some people have had it most of their lives. Long term, low-grade depression is also known as dysthymia. Dys, meaning disorder, and thymia meaning mood. Dysthmia is then a disorder of ones mood. The last type is manic depression. The lows of this depression can alter with days or weeks of maniaextreme feelings, unreasonable thoughts, and inappropriate, sometimes destructive behavior. The manic-depressive person fluctuates from one emotional pole to another, often in rapid swings. 3 There are many symptoms of depression. Symptoms can include persistent sad or “empty” mood, loss of interest or pleasure in ordinary acti .....