什么是顺反子?用“互补”和“等位基因”说明“基因”这个概念。
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两个连锁基因的连锁强度______,那么测交出来的遗传距离越大。如果一个杂合体自交或测交均分离不出新类型,那
Questions 18 to 20 are based on the following Passage. At the end o f the Passage, you will be given 15 seconds to answer the questions.
Now, listen. to the passage.
The purpose of Magellan's expedition was
[A] to sail round the world.
[B] to find navigation lane from the Atlantic to the Pacific.
[C] to make a voyage to Asia.
[D] to carry men to Philippines.
下列四个百分条图中,能够正确表示该师四个团中除菌痢外的传染病发病人数占该传染病发病总人数的比例的一个是()。
在染色体结构变异中,缺失和重复导致染色体上基因______发生了变化,而倒位和易位导致染色体上基因的______发