Concept Check 21.1
d.
Which of the following statements about virus structure is true? a. DNA is the genetic material in all viruses. b. The capsomere is made up of small protein subunits called capsids. c. All viruses are encased in a viral membrane. d. Glycoproteins help the virus attach to the host cell.
A third hypothesis; suggests that viruses may have originated from self-replicating entities similar to transposons or other mobile genetic elements.
What is the self-replicating hypothesis?
They come in many shapes and sizes
What types of shapes are viruses?
Nucleic acid core with an outer protein coating
Viral morphology is very simple. What parts make up a virus?
The second hypothesis, suggest that viruses originated from RNA and DNA molecules that escaped from a host cell
What is the escapist/the progressive hypothesis?
(a) helical, (b) polyhedral, or (c) have a complex shape.
How can viral capsids be shaped?
Type of capsid
In the past, when viruses were classified based on morphology, which of the following features was used to classify viruses?
Regressive (aka devolution)
The observation that the bacteria genus Chlamydia contains species that can only survive as intracellular parasites supports which viral origin hypothesis?
Capsomeres
The proteins of the capsid are encoded in the viral genome, and are called ...
d.
Which statement is true? a. A virion contains DNA and RNA. b. Viruses replicate outside the cell. c. Most viruses are easily visualized with a light microscope d. Viruses are acellular.
Viruses do not have ribosomes.
Why is the sequence of the 16s rRNA not useful in virus classification?