可引起禽类肿瘤性疾病的双股DNA病毒是（） A.鸡痘病毒 B.新城_爱下问搜题

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问题单项选择题 A1型题

可引起禽类肿瘤性疾病的双股DNA病毒是（）

A.鸡痘病毒

B.新城疫病毒

C.禽流感病毒

D.马立克氏病毒

E.传染性法氏囊病病毒

答案

参考答案：D

解析：主要的动物病毒，疱疹科病毒马立克氏病病毒（MDV）：学名禽疱疹2型，是鸡的重要的传染病病原，具有致肿瘤特性。其主要特征是外周神经发生淋巴样细胞浸润和肿大，引起一肢或两肢麻痹，各种脏器、性腺、虹膜、肌肉和皮肤也发生同样病变并形成淋巴细胞性肿瘤病灶。病毒基因组为线状双股DNA。【考试科目】《兽医微生物学与免疫学》

填空题

把9米长的绳子平均截成5段，每段是这根绳子的（），每段长（）米。

单项选择题

A certain type of shrimp habitually hovers around superheated deep-sea geysers, near which the bacteria that form the shrimps diet can be found. Because the geysers emit a faint light, scientists have concluded that the shrimps’ light sensitive dorsal patches were developed to locate the geysers and thereby find food.
Which of the following, if true, casts the most doubt on the scientists’ conclusion

A．The light to which the shrimps are sensitive is not the sort of light that the geysers emit.

B．The light given off by the geysers too faint to be detected by the human eye.

C．The heat inside a geyser’s stream is sufficient to kill instantly any bacteria that move into it.

D．Most other types of shrimp use eyes located at the end of eyestalks in order to see.

E．(E) In other types of shrimp a heat-sensing organ has developed that could serve the same geyser-detecting purposes as the light sensitive patches are said to serve.