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Beyond Viruses……
Can create an “infection” that can lead
to the death of the “infected organism?
…appears to be able to replicate itself…
…is not a bacteria!
…is smaller than a virus?
…is not a virus!
…contains genetic information!
…structurally like the “guts”of a virus!
VIROIDS: The Plant Invaders…
A VIROID is a…
VIR(virus)OID(like) particle.
Viroids are“sub-viruses” composed
exclusively of a single circular strand
of nucleic acid (RNA) that codes for a
single protein.
VIROIDS: DID YOU KNOW VIROIDS…
•are infectious particles.
•are smaller than any of the known
viruses.
•range in size from approximately 20 nm
(8 x 10-7 inches) ...
•are just 100 times larger than Atoms
which measure in at .1 nanometers.
•cause certain plant and human diseases.
•consists only of Nucleic Acid (RNA) .
VIROIDS: The Potato “Nose”…
Normal
Potatoes
Infected
Potatoes
VIROIDS: The Potato “Nose”…
In Class Reading…
VIROIDS!
VIROIDS : Are VIROIDs a new form of life?
1- Are VIROIDs made of cells?
NO
2- Are VIROIDs organized?
YES
3- Do VIROIDs use energy?
NO
4- Are VIROIDs responsive?
NO
VIROIDs : Are VIROIDs a new form of life?
5- Do VIROIDs grow? (enlarge and divide)
NO
6- Do VIROIDs reproduce?
YES
~they recruit their host’s cellular machinery to
replicate it RNA using the original as a
template
7- Do VIROIDs adapt?
YES/NO,
~ do mutate into other viable forms.
VIROIDs : Are VIROIDs a new form of life?
8- Do VIROIDs die?
NO,
however like all nucleic acids, their structure
can be degraded by catalysts or UV light
9- Do VIROIDs come from pre-existing
viroids?
YES
~ existing VIROIDs are the templates for the
next generation of replicants
VIROIDs : Origin & Structure
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