Balance the tubes by adding isopropanol or extraction buffer. Produce a pellet of DNA by centrifuging at 15,000 rpm for 15 min. Gently pour off the supernatant and lightly dry the pellets by inverting the tubes on paper towels for 1-2 min.
Onions not only provide flavor, they also provide important nutrients and health-promoting phytochemicals. High in vitamin C, onions are a good source of dietary fiber, and folic acid. They also contain calcium, iron, and have a high protein quality (ratio of mg amino acid/gram protein). Onions are low in sodium and contain no fat. Onions contain quercetin, a flavonoid (one category of antioxidant compounds).
Iron plays a central role in the function of red blood cells which help in transporting oxygen around the body, in energy production and DNA synthesis. Spinach is also an excellent source of vitamin K, vitamin A, vitamin C and folic acid as well as being a good source of manganese, magnesium, iron and vitamin B2. Vitamin K is important for maintaining bone health and it is difficult to find vegetables richer in vitamin K than spinach.