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Nucleotides in DNA

The study of modern genetics depends on an understanding of the physical and chemical characteristics of DNA. Some of the most fundamental properties of DNA emerge from the characteristics of its four basic building blocks, called nucleotides. Knowing the composition of nucleotides and the differences between the four nucleotides that make up DNA is central to understanding DNA’s role in living systems.

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The immunity diet

Everybody knows that broccoli are a healthy food. Like most vegetables, they bring in vitamins, antioxidants, and fiber that contribute to a complete diet, protect our tissues from oxidative damage, and regulate the activity of the intestine. Now two recent studies in mice, highlighted on the New England Journal of Medicine January 12 issue, show that broccoli and related veggies (cabbage, brussel sprouts, kale) do more than that: they directly and specifically stimulate the development of immune system cells in the wall of the intestine, to protect us from infections, to control the amount of bacteria present in the gut, and to modulate inflammation.

Here is the cool, geeky part: the effect involves chemicals called flavonoids, present at high levels in Broccoli & Co., and a protein, the Aryl hydrocarbon Receptor, located in a small population of lymphoid cells in the intestinal wall. Flavonoids bind to the AhR and stimulate limphoid cell growth, and these cells in turn stimulate the growth of other immune system structures called lymphoid follicles. These structures and their products provide immunity against pathogens, and regulate the inflammatory response. Mice without the AhR weaned with a flavonoid-rich diet have few lymphoid follicles and low immunity against infection, same as mice with the AhR but weaned with a diet free of flavonoids.

Important? Yes, because this is the first time that direct immunomodulation by dietary plant compounds has been shown, and it should stimulate more studies on the effects of diet on the immune system. So are new guidelines coming soon on how to put together the perfect “immune-boosting diet”? Well, maybe not so soon, because mice ain't people, and the USDA needs human studies to issue guidelines; but mice are more similar to us than most of us like to acknowledge, broccoli. taste pretty good and are already known to be a healthy food, so why not crank them up a bit?

Albedo

The energy that warms Earth’s atmosphere comes from the Sun, but sunlight does not warm the atmosphere directly. The atmosphere warms from below. Most of the short wavelength, electromagnetic energy from the Sun passes through the atmosphere and is absorbed by the Earth. Absorbing this energy warms the Earth. As the Earth warms, energy re-radiates back into the atmosphere as heat. Eventually, this energy re-radiates from the atmosphere back out into space.

The Earth does not absorb all of the electromagnetic energy that hits it. Some reflects back out into space. This is important for the Earth’s energy balance because only absorbed energy contributes to the temperature of the Earth/atmosphere system. The amount of energy reflected by an object is its Albedo.
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