National parks are large areas of public land. They give a safe home to local plants and animals. They help keep the air and water clean. They also give us the best trips. Today, there are about 7,000 national parks around the world. Forbes has listed 12 of the most beautiful ones in the world that will surprise you with their amazing landscape, geographic wonders and colourful plants and animals.

    The Grand Canyon National Park of the US is one of the natural wonders of the world. It is best known for its size and depth. It is 446 kilometres long, up to 29 kilometres wide, and 1.6 kilometres deep. The immensity of the canyon makes people feel they are very small. Every year, about 5 million people visit here. Taking a tour in the South Rim offers visitors the park's full views, while the North Rim shows beautiful wild flowers

    If you love animals, you'll like the Serengeti National Park in Tanzania. The "Big Five" live here. They are the lion. African elephant, African leopard, rhinoceros and African buffalo. The name "Big Five" came from the five animals that were the hardest to catch. Now they are what people most want to see in the wild. If you visit the park, you should never miss the migration (迁徙) of over 1.5 million wildebeest (牛羚) and 250,000 zebras every year. This is the most famous site of the park.

    It took 13 years of international effort to map the human biological blueprint of all the genes (基因) that make us different people. The first rough draft (草图) made in 2000. The last of our 23 chromosomes (染色体) was clearly described in 2006. Ever since then, the age of personal genetic testing has been upon us. Since that time, a growing number of private companies have come on the market mostly through the Internet, offering to scan your personal DNA and compare it to some disease markets of the blueprint, called DTC genetic tests.

    But over the last five years the medical world has been discussing excitedly about whether these DTC tests are helpful or harmful, scientifically believable or completely useless. One of the usual criticisms (批评) is that the science is so new that no one really knows yet how to explain the information.

    "At present they largely remain in the period of research studies," notes Dr. Greg Ferro, special advisor to the director of genomic medicine at the US National Human Genome Research Institute. Ferro says there are two reasons." The first is that when they offer a test, are they really checking what they should check? And then the next is that even if it is believable, does what the test is checking really mean anything to your health?"

    Other worries include the privacy of the results and how your personal genetic information might be used by insurance (保险) companies to refuse your insurance or your boss to dismiss you. Or you could learn information with a huge social or personal impact (冲击), such as finding out that genetically you cannot possibly be the father of your child. It can also give you risks that may break your life, such as whether you are at high risk of cancer, Parkinson or other terrible diseases.

    Criticisms over the tests are such that some countries, such as Germany, have banned them. In 2011, some scientists advised the US government that most tests should be done under the guidance of medical professionals (专家). The UK government also expressed its worries about DTC genetic tests and in August 2010 made a set of rules to guide the development of genetic tests.

    In 2011, three medical researchers published a review article in the International Journal of Clinical Practice, saying that such tests offered more risks than benefits. The most important reason is that the tests might create worries or unreal results or drive unnecessary medical treatments. They also noted some of the genetic information the tests are based on at present is far from being perfect.