Chapter 24: Virus
Some viruses arer thought to induce ____________, a disease characterized by uncontrolled cell division
Cancer
The protein coat of a virus is called a
Capsid
All viruses reproduceby taking over the reproductive machinery of a
Cell
Which of the following human activities is most closely associated with the emergence of viruses not previously seen in humans
Clearing of forests for housing
All viruses do not have
Cytoplasm, mitochondria and ribosomes
Which of the following is not linked to cancer
Ebola Virus
In which cell cycles do viral DNA become integrated into the host cells DNA
Lysogenic
Viruses that infect a host cell and have their nucleic acid replicated but do not harm the host cell are in a __________ cycle
Lysogenic
In the _______ cycle viruses destroy the host cell
Lytic
which of the following has been the most successful at fighting viral diseases
Vaccination and Vector control
Explain why viruses are not considered to be living organisms
Viruses are not living because threy are not cellualar, cannot reproduce outside the host cell and cant make their own proteins
A typical virus consists of
a protein coat and a nucleic acid core
Which of the following contains only RNA
a viroid
Most scientists believe that viruses first appeared on the earth ________ living cells appeared
after
Antibiotics are ineffective against viral infection because
antibiotics interfere with cellular processes that viruses do not perform
Unlike viruses, prions
are composed only of protein
Bacteriophages
are viruses that infect bacteria and a have a polyhedral head and a helical tail
Biologists now know that viruses
contain RNA or DNA in a protein or lipid protein coat
Scientists first began to study viruses becasue they
could not be seen but they were causing disease
Most scientists think that early viruses originated from
existing cell plants
HIV causes AIDS by
gradually destroying a persons immune system
Which of the following is not a vector of viral diseases
prions
The capsid of virus is the
protective outer coat
Viruses
reproduce only in living cells
A virus that transcribes DNA from an RNA template is called
retrovirus
Viruses that use reverse transcriptase to cause their host cells to transcirbe DNA from an RNA template are called
retroviruses
Viruses can vary in size and
shape
Animal viruses often infect only specific host cells because
the host cell must have specific receptors for proteins on the virus surface
Why are viruses nontheless included in the study of biology
they are included because they are acvctive inside living cells
Viruses are considered nonliving because
1) They cannot reproduce by themselves, 2) they are not made up of cells 3) They cannot carry out metabolism by themselves
Tobacco masaic virus
1) are able to be crystallized 2) cause disease in tobacco plants and 3) and are smaller than bacterium
Viruses are classified according to
1) whether they contain RNA or DNA 2) the shape of their genome 3) whether they have a membrane envelope
which of the following are viral diseases of humans
Hepatitis, SARS, and shingles
An enzyme called _____________ _______________ manufactures DNA that is complementary to a virus's RNA
Reverse Transcriptase
Chickenpox and __________ are caused by the same virus
Shingles
The study of Viruses is a part of biology because
They are active inside living cells
