The causal organism of dengue fever is a mosquito-borne virus which belongs to which one among the following categories?
- A.Flavi-ribo virus
- B.Adenovirus
- C.Vaccinia virus
- D.Nipah virus
Correct answer
Explanation
The correct answer is A, Flavi-ribo virus. Dengue virus is a flavivirus, an RNA (ribonucleic acid) virus of the family Flaviviridae.
Dengue is spread mainly by the bite of the female Aedes aegypti mosquito, which breeds in clean, stagnant water and bites during the day. The virus has four serotypes, DEN-1 to DEN-4, so a person can get dengue more than once, and a second infection by a different type can cause severe dengue with bleeding. Common signs are high fever, severe pain behind the eyes, joint and muscle pain (hence 'breakbone fever'), rash and a fall in platelet count. Yellow fever, Zika, Japanese encephalitis and West Nile fever are caused by related flaviviruses.
B is wrong because adenoviruses are DNA viruses that mostly cause colds, sore throat and conjunctivitis. C is wrong because vaccinia is the pox virus used in the smallpox vaccine. D is wrong because Nipah is a henipavirus spread by fruit bats and pigs, not by mosquitoes.
Exam tip: Dengue, yellow fever, Zika and chikungunya are all spread by Aedes mosquitoes.
Practice Questions
View allWhich one of the following features is an indication for modification of stem of a plant?
- A.Presence of 'eye' on potato
- B.'Scale' found in onion
- C.'Tendril' found in pea
- D.'Hair' present in carrot
Show answer
The eyes of a potato are nodes with buds, and only a stem bears nodes and buds, so they prove that the potato is a modified stem.
Read the full explanation →Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?
- A.Tungsten
- B.Copper
- C.Rubidium
- D.Aluminium
Show answer
Rubidium, an alkali metal like caesium, gives off electrons easily when light falls on it, so it is used in photoelectric cells.
Read the full explanation →Tooth enamel is made up of which one of the following calcium compounds ?
- A.Calcium carbonate
- B.Calcium sulphate
- C.Calcium hydroxide
- D.Calcium phosphate
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Tooth enamel is made mainly of calcium phosphate in the form of a hard crystal called hydroxyapatite. Enamel is the hardest substance in the human body, harder even than bone.
Read the full explanation →Which one of the following viruses used to be responsible for highly infectious disease Smallpox ?
- A.Adenovirus
- B.Variola virus
- C.Aichi virus
- D.Coxsackie virus
Show answer
Smallpox was caused by the variola virus, a large DNA virus of the pox family that spread from person to person through the air.
Read the full explanation →After fertilization, the fruit and the seed are produced by
- A.ovule and ovary, respectively
- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
Show answer
After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
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