TAMU BIO 112 EXAM 2- Viruses
Questions with Quality Answers 2026
Updated.
Background on viruses - Answer -parasitic like entities
- can NOT fit into any domain of life
- infect almost all known organisms from bacteria, to plants, and animals
- non-cellular, not metabolism, no growth, no cell division
- can copy or replicate
- completely dependent on host for resources to produce progeny
viruses can cause dozen of ailments in humans ranging from... - Answer mild illness to serious
disease
Did viruses exist before they were seen? - Answer Yes (visible by microscopy)
Size and Imaging - Answer -almost to small to be seen with light microscopes
-single virus particle (viron) maybe only 20nm across
-electron micro. can magnify 500,000x +
-electron micro. led to many types of viruses in many type of organisms.
What do viruses depend on to make copies of themselves? - Answer Host Cells
Viruses are... - Answer -Acellular, they're not cells
- origin is uncertain
-collected pieces of nucleic acid from various sources
-the ultimate parasite; can not replicate UNLESS they're in a host cell using the cells machinery
Evolution of viruses - Answer - no known fossil records
-speculate using biochemical/ genetic info
3 main evolutionary hypotheses - Answer 1. REGRESSIVE: were once small cells that
parasitized larger cells
SUPPORT- discovery of giant viruses with similar DNA to parasitic bacteria
PROBLEM- does not explain why the smallest of cellular parasite do not resemble viruses
, 2. ESCAPIST: evolved from bits of DNA/RNA that escaped from genes of larger organisms
PROBLEM: does not explain structures that are unique to viruses and are not seen as cells, such
as complex capsids.
3. VIRUS FIRST: evolved from complex molecules of protein and nucleic acid before cells 1st
appeared on earth (implies that viruses contributed to rise of cellular life)
SUPPORT: viral genomes encode proteins that do not have cellular homologs.
PROBLEM: violates definition of viruses, in that they require host cell to replicate.
Do viruses have high evolution/rate of mutation? - Answer yes
All viruses contain two components - Answer 1. Nucleic acid genome
-DNA or RNA
2.Protein capsid
-covers the genome
Virus characteristics - Answer -obligatory INTRAcellular parasites
-no ribosomes
-no ATP generating mechanism
-many viruses are medically important
Viruses have genomes - Answer -virus core contains nucleic acid
-either DNA/RNA (not both)
-single or double stranded
-circular or linear
-one piece of multiple segments
-the genome is much smaller than cell genomes
DNA Viruses - Answer viral DNA directs host to synthesize new copies of its genome and to
translate and transcribe them into viral genomes
-less chance for error
human infections: chicken pox, HEP B, HPV
Questions with Quality Answers 2026
Updated.
Background on viruses - Answer -parasitic like entities
- can NOT fit into any domain of life
- infect almost all known organisms from bacteria, to plants, and animals
- non-cellular, not metabolism, no growth, no cell division
- can copy or replicate
- completely dependent on host for resources to produce progeny
viruses can cause dozen of ailments in humans ranging from... - Answer mild illness to serious
disease
Did viruses exist before they were seen? - Answer Yes (visible by microscopy)
Size and Imaging - Answer -almost to small to be seen with light microscopes
-single virus particle (viron) maybe only 20nm across
-electron micro. can magnify 500,000x +
-electron micro. led to many types of viruses in many type of organisms.
What do viruses depend on to make copies of themselves? - Answer Host Cells
Viruses are... - Answer -Acellular, they're not cells
- origin is uncertain
-collected pieces of nucleic acid from various sources
-the ultimate parasite; can not replicate UNLESS they're in a host cell using the cells machinery
Evolution of viruses - Answer - no known fossil records
-speculate using biochemical/ genetic info
3 main evolutionary hypotheses - Answer 1. REGRESSIVE: were once small cells that
parasitized larger cells
SUPPORT- discovery of giant viruses with similar DNA to parasitic bacteria
PROBLEM- does not explain why the smallest of cellular parasite do not resemble viruses
, 2. ESCAPIST: evolved from bits of DNA/RNA that escaped from genes of larger organisms
PROBLEM: does not explain structures that are unique to viruses and are not seen as cells, such
as complex capsids.
3. VIRUS FIRST: evolved from complex molecules of protein and nucleic acid before cells 1st
appeared on earth (implies that viruses contributed to rise of cellular life)
SUPPORT: viral genomes encode proteins that do not have cellular homologs.
PROBLEM: violates definition of viruses, in that they require host cell to replicate.
Do viruses have high evolution/rate of mutation? - Answer yes
All viruses contain two components - Answer 1. Nucleic acid genome
-DNA or RNA
2.Protein capsid
-covers the genome
Virus characteristics - Answer -obligatory INTRAcellular parasites
-no ribosomes
-no ATP generating mechanism
-many viruses are medically important
Viruses have genomes - Answer -virus core contains nucleic acid
-either DNA/RNA (not both)
-single or double stranded
-circular or linear
-one piece of multiple segments
-the genome is much smaller than cell genomes
DNA Viruses - Answer viral DNA directs host to synthesize new copies of its genome and to
translate and transcribe them into viral genomes
-less chance for error
human infections: chicken pox, HEP B, HPV
