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外表相同的个体，有时会产生完全不同的后代，这主要是外界条件影响的结果。
根据孟德尔遗传规律，一对基因是杂合的个体能够产生两种配子，该个体自交能够产生三种基因型的个体。假如该杂合体涉及”对基因，能够产生______种配子，自交后能够产生______种基因型的个体。
在AaBbCcDd×aaBbCcDd杂交中，各基因互不连锁，则子代中表型与aaBbCcDd亲本相同的个体的概率是______。
Feed the World with Potatoes1 As food prices continue to rise rapidly, there is growing concern about the effect it will have among the world"s poor.2 Increasingly, experts are looking to the potato as a possible low-cost solution to feeding the hungry. To emphasize the issue, the United Nations has called the potato "a hidden treasure", and named 2008 the International Year of the Potato. Here"s how potatoes could end the food crisis.3 The potato matures more quickly, on less land and in harsher climates than most other major crops. Up to 85 percent of the plant is eatable, compared with around 50 percent of cereals. Its broad adaptability to a wide variety of farming systems is also noteworthy.4 Potatoes are an excellent source of complex carbohydrates ( 碳水化合物), which release their energy slowly, and have only 5 percent of wheat"s fat content. They contain only a quarter of the calories of bread and, according to the Potato Center, when boiled, potatoes have more protein and nearly twice the calcium (钙) as corn. Additionally, they are good sources of vitamin C, iron, potassium (钾) and zinc (锌).5 The Food and Agricultural Organization recently surveyed food price inflation in over 70 of the poor countries. Cereal price inflation was much higher and far more widespread than for potatoes. A significant factor behind the potato"s affordability is the fact that unlike other agricultural products, the potato is not yet a global commodity, and has therefore not attracted speculative investors. Raw potatoes are heavy and can rot during transit, so global trade has been slow to take off. Also, potatoes are susceptible (易受影响的) to infection with disease, hindering (阻碍) export. According to analysts" estimates, less than 5 percent of potatoes are traded internationally, with prices driven primarily by local tastes instead of international demand. Paragraph 3 ______
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