Four bands appear in gel electrophoresis. Gel electrophoresis is an experimental method used to separate mixtures of DNA, RNA, or proteins by molecular size.
DNA is negatively charged, so when a current is applied to the gel, the DNA migrates towards the positively charged electrode. Fragments are ordered by size because short DNA strands migrate through the gel faster than long strands. There are some basic steps for performing gel electrophoresis outlined below. 1) pour the gel, 2) prepare the sample, 3) load the gel, 4) run the gel (expose it to an electric field), 5) stain the gel. Gel electrophoresis is a technique for separating biomolecules by size. Separation of these molecules is achieved by placing them in a small pore gel and creating an electric field across the gel
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The correct answer would be:
<em>Cycles.</em>
Answer: Land, Water,Urbanization, and smog and acid rain.
Explanation:
Smog and acid rain are produced through similar sources, primarily vehicle and industry emissions. Though both result from human-caused air pollutants, there are chemical distinctions between the two. Though there are regulations in effect to reduce both types of pollution, they remain a threat to both human health and the environment.Smog Causes A combination of three components -- nitrogen oxides, volatile organic compounds (VOCs) and sunlight -- causes smog. Nitrogen dioxide interacts with sunlight to create nitrogen oxide and a free oxygen molecule. This interaction produces ozone, which typically turns back into nitrogen dioxide, and the cycle repeats. The addition of VOCs interrupts the cycle, however. VOCs are produced by various sources, such as paint, cleaning products and refrigerants. The VOCs prevent the breakdown of ozone, allowing it to gather near the surface of the Earth, where even more nitric oxides are produced by vehicle and industry emissions, creating the dense smog seen in large cities such as Los Angeles and Beijing.Smog Hazards The presence of ozone in the form of smog can have several negative health effects. Respiratory systems can be irritated, reducing overall lung function and triggering asthma attacks. Evidence reported by the Environmental Protection Agency also suggests exposure to ozone reduces immune system responses, especially in the lungs. These effects subside over time, but little is known about the long-term effects of repeated exposure. Vegetation also suffers from smog, as plants that take up too much ozone can be damaged in ways such as discoloration and a loss of leaves that cuts photosynthesis efficiency by up to 50 percent.
