MIDTERM BIOC20 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS GRADED A++ LATEST UPDATE
Virion consists of
-Nucleic acid genome
-protective protein coat
-Some contain a lipid envelope
Virion capsid
Protective protein coat
Nature of Viruses
Obligate intracellular parasites (only replicate in living cell)
Viruses lack
Essential functions
-synthesis of basic biological building blocks (nucleotides, amino acids, CHO's, lipids)
-generation of ATP
-protein synthesis (ribosomes, tRNAs)
Uncoating
First step, virus particles break down and release genomes inside the cell
-released from protective protein shell
Once virus uncoats
Genome can be used as a template for mRNA synthesis - produce proteins
Newly made viral proteins
,Work together to replicate genome, encapsulate the new genomes to form progeny
virions
Virus morphology
Distinct, genome sizes, and particle sizes
-smallest 20 nm in diameter, coding few as 2 proteins
-largest 500nm in diameter, coding > 1200 proteins
Virus genomes can be
-RNA or DNA, not both
-single or double stranded
-circular or linear
Problem with RNA genome
-no RNA polymerase - replication problem
-difficulty making RNA transcript
Viruses can infect
All forms of life, animals, plants, insects, bacteria, algae,, fungi
Most abundant form of life
Viruses, 10 fold excess of virus compared to bacteria in earth oceans
Mass = 1 million blue whales
Length - 200 million light years
Study of viruses led to
Identification of promoters for eukaryotic RNA polymerase
Enzymes involved in cellular DNA replication
RNA splicing from studying viral mRNAs in eukaryotic cells
,Isolation of numerous cellular oncogenes and the understanding that cancer is caused
by their mutation or unregulated expression
First virus discovered
TMV
First virus discovered by
Distinguished by filtration
Russian scientist Dimitri Ivanovski
Dutch scientist Martinus Beijerinck (first name for virus = contagious virus fluidium)
TMV
Tobacco mosaic disease killing tobacco plants
Found by grounding up infected leaves trying to filter bacteria, passed through porcelain
filter was infecting leaves
Discovery about viruses in mid 1930s
Highly purified TMV could form crystals
-challenged conventional notions about genes and nature of living organisms
Are virsuses alive?
Not living entities, biochemical processes - only living period inside host
1915-1917 scientist in England and France discovered bacteria
Could be listed by filterable agents
Study of bacteriophages helped establish the field of molecular biology by
Mapping phage genes
Elucidated phage replication cycles
Developed the plaque assay
, Bacteriophage
Viruses that infect bacteria
Felix d'Herelle
Worked on phage therapy
-using phage to treat human bacterial disease
-useful against antibiotic resistant bacteria
-use as antibacterial agents in humans is not accepted
Tumor virus study lead to
Understanding of nature of cancer
-reverse transcriptase
-oncogenes
Now being used to construct vectors to express proteins to specifically destroy tumor
cells
Plaque assay allows for
Quantitation of virus
-based on principle that bacteria diffract visible light, dense liquid cultures appear
'cloudy'
-bacteriophages lyes their host cell and this lysis causes a loss of diffraction, leading to
a clearing of bacterial culture ('clear lysis' = plaque)
Reported as PFU (plaque forming unit)
Method of virus detection and measurement
Spread bacteria on surface of nutrient agar (Petri dish) nd apply serial dilutions of a
phage suspension
COMPLETE SOLUTIONS GRADED A++ LATEST UPDATE
Virion consists of
-Nucleic acid genome
-protective protein coat
-Some contain a lipid envelope
Virion capsid
Protective protein coat
Nature of Viruses
Obligate intracellular parasites (only replicate in living cell)
Viruses lack
Essential functions
-synthesis of basic biological building blocks (nucleotides, amino acids, CHO's, lipids)
-generation of ATP
-protein synthesis (ribosomes, tRNAs)
Uncoating
First step, virus particles break down and release genomes inside the cell
-released from protective protein shell
Once virus uncoats
Genome can be used as a template for mRNA synthesis - produce proteins
Newly made viral proteins
,Work together to replicate genome, encapsulate the new genomes to form progeny
virions
Virus morphology
Distinct, genome sizes, and particle sizes
-smallest 20 nm in diameter, coding few as 2 proteins
-largest 500nm in diameter, coding > 1200 proteins
Virus genomes can be
-RNA or DNA, not both
-single or double stranded
-circular or linear
Problem with RNA genome
-no RNA polymerase - replication problem
-difficulty making RNA transcript
Viruses can infect
All forms of life, animals, plants, insects, bacteria, algae,, fungi
Most abundant form of life
Viruses, 10 fold excess of virus compared to bacteria in earth oceans
Mass = 1 million blue whales
Length - 200 million light years
Study of viruses led to
Identification of promoters for eukaryotic RNA polymerase
Enzymes involved in cellular DNA replication
RNA splicing from studying viral mRNAs in eukaryotic cells
,Isolation of numerous cellular oncogenes and the understanding that cancer is caused
by their mutation or unregulated expression
First virus discovered
TMV
First virus discovered by
Distinguished by filtration
Russian scientist Dimitri Ivanovski
Dutch scientist Martinus Beijerinck (first name for virus = contagious virus fluidium)
TMV
Tobacco mosaic disease killing tobacco plants
Found by grounding up infected leaves trying to filter bacteria, passed through porcelain
filter was infecting leaves
Discovery about viruses in mid 1930s
Highly purified TMV could form crystals
-challenged conventional notions about genes and nature of living organisms
Are virsuses alive?
Not living entities, biochemical processes - only living period inside host
1915-1917 scientist in England and France discovered bacteria
Could be listed by filterable agents
Study of bacteriophages helped establish the field of molecular biology by
Mapping phage genes
Elucidated phage replication cycles
Developed the plaque assay
, Bacteriophage
Viruses that infect bacteria
Felix d'Herelle
Worked on phage therapy
-using phage to treat human bacterial disease
-useful against antibiotic resistant bacteria
-use as antibacterial agents in humans is not accepted
Tumor virus study lead to
Understanding of nature of cancer
-reverse transcriptase
-oncogenes
Now being used to construct vectors to express proteins to specifically destroy tumor
cells
Plaque assay allows for
Quantitation of virus
-based on principle that bacteria diffract visible light, dense liquid cultures appear
'cloudy'
-bacteriophages lyes their host cell and this lysis causes a loss of diffraction, leading to
a clearing of bacterial culture ('clear lysis' = plaque)
Reported as PFU (plaque forming unit)
Method of virus detection and measurement
Spread bacteria on surface of nutrient agar (Petri dish) nd apply serial dilutions of a
phage suspension
