MediumBiologyHigh School (11–12)Diversity of Living Organisms › Viruses, Viroids and PrionsConceptualBoard Exam
Put these in order and say what each showed: Stanley crystallised a virus; Ivanowsky found that the…
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Put these in order and say what each showed: Stanley crystallised a virus; Ivanowsky found that the cause of tobacco mosaic passed through a bacterial filter; Diener found the viroid; Beijerinck called the cause a contagious living fluid. How many years passed from Ivanowsky's work to Stanley's? From Stanley's to Diener's?
Need a reminder? The key ideaShow
Viruses, viroids and prions are not in the five kingdoms. A virus is an obligate parasite: DNA or RNA, never both, inside a protein capsid. Ivanowsky (1892) found that the cause of tobacco mosaic passed through a bacterial filter; Beijerinck (1898) called it Contagium vivum fluidum; Stanley (1935) crystallised the virus. Diener (1971) found the viroid, free RNA with no coat. A prion is an abnormally folded protein (BSE, CJD).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The order. Ivanowsky (1892): the cause is smaller than a bacterium. Beijerinck (1898): Contagium vivum fluidum. Stanley (1935): viruses can be crystallised. Diener (1971): the viroid, free RNA.
Step 2. The gaps. years, and years.
Answer: Ivanowsky, Beijerinck, Stanley, Diener; years and years.
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