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Author Question: Center-based classrooms refer to classrooms that are developed around learning centers. Indicate ... (Read 88 times) |
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.