Lesson 2

1. Lesson 2
Завдання до уроку з теми “Viruses, Viroids, Prions”
Students have to read the information about viruses and viroids and fill in the
chart
Viruses Viroids: the plant invaders!
A virus is an infectious agent with
both living and non-living characteristics
that is totally dependent on a host cell
for replication.
Viruses contain only either DNA or
RNA (but not both), and a protein coat,
which encases the nucleic acid.
They have no homeostasis,
metabolism, no respond to the stimuli,
and they don’t grow or develop. They are
able to infect all organisms.
A viroid is a VIR (virus) OID
(like) particle, a “sub-virus” composed
exclusively of a single circular strand of
nucleic acid (RNA). In other words,
Viroids are small, circular RNA
molecules without a protein coat.
Viroids infect plants only!
Task 1 Fill in the chart with the characteristics which describe viruses, viroids, or both.
Virus vs viroid
Needs host cell to reproduce, protein coat, no protein coat, infectious agent, DNA and RNA, RNA, infects
all organisms, infects plants, no cell, needs host cell to reproduce
viruses viroids

2. Keys
Viruses:
Protein coat
DNA RNA
Infect all organisms
Both:
Infectious agent
No cells
Need host cells to reproduce
Viroids:
No protein coat
RNA
Infect plants
Task 2: LISTENING FOR COMPREHENSION : Listen to the text and fill in the chart
Characteristics of prion diseases and the specific properties of causative agents
Infection-carrying proteins are called prions. They have neither DNA nor
RNA. It appears that they cause fatal human brain diseases. Years may pass
between getting infected and having symptoms, as the incubation period lasts
from months to years, while the progressive course lasts from weeks to months.
What makes these diseases especially dangerous is the fact that there is no
immune response, so that it makes it almost impossible to detect them. If
detected, prion diseases have no specific treatment.
The causative agents have no detectable nucleic acid. They are resistible to
alcohol, formalin, heat, and UV irradiation.

3. Characteristics of prion disease Student’s answers
Incubation period
Progressive course
Host immune response
Specific treatment
Keys
Characteristics of prion disease Student’s answers
Incubation period From months to years
Progressive course From weeks to months
Host immune response no
Specific treatment no
Task 3: Listen to the text for the second time and fill the gaps while listening
Characteristics of prion diseases and the specific properties of causative agents
Infection-carrying proteins are called _______. They have ____ DNA __
RNA. It appears that they cause _____ human _______ diseases. Years may pass
between _______________ and _________________, as the incubation period
lasts from _______________, while the progressive course lasts from
_______________.
What makes these diseases especially dangerous is the fact that there is no
___________________, so that it makes it almost impossible to _________ them.
If detected, prion diseases have no ____________________.
The causative agents have no detectable _______________. They are
resistible to alcohol, formalin,______, and UV ____________.