Genetics of viruses and bacteria Flashcards
what are pathogens?
agents that cause disease symptoms in their hosts
what are some general properties of virus?
a virus is a small nonliving particle with a nucleic acid genome enclosed in a protein, they are non-living.
first virus discovered?
Tobacco Mosaic Virus (TMV)
first human virus?
virus that causes yellow fever
what is a cell that is infested by a virus called?
host cell
what is host range?
number of species and cell types can be infected
all viruses have a _____ (protein coat) that varies in shape and complexity
capsid
capsids are composed of one or more protein subunits called?
capsomers
capsids have a variety of shapes which are?
helical and polyhedral
what helps viruses bind to their host cell?
glycoproteins
what are bacteriophages?
viruses that infect bacteria
when a virus infects a host cell, expression of viral genes leads to?
viral reproductive cycle
what are the 5=6 common steps in a viral reproductive cycle?
Attachment, Entry, Integration (*), Synthesis of viral components, Viral assembly and Releases
what is viral envelope derived from?
host cell plasma membrane
what does integrase do?
Integrase cuts host chromosomal DNA and inserts viral genome
what is phage in bacterial DNA called?
prophage
what is the lysogenic cycle?
the phase of viral reproductive cycle when prophage is integrated into chromosome, no new phages made and prophage can be excised from bacterial chromosome to end the cycle
what type of virus is HIV?
an RNA virus.
once integrated, the viral DNA is a?
provirus
viruses that follow the integration mechanism are?
retroviruses
in HIV, the DNA provirus is not excised from host chromosome, but instead?
it is transcribed in the nucleus to produce many copies of viral RNA.
what translates mRNA?
host cell ribosomes
what does it mean when viruses self-assemble?
they spontaneously bind to each other to form a complete virus particle
what are the two stages of assembly of HIV?
- Capsid proteins assemble around 2 molecules of viral RNA
and molecules of reverse transcriptase and integrase - Next the newly formed capsid acquires its outer envelope in a budding process
Assembly of phage I requires the help of?
noncapsid proteins
After phage assembly, a phage-encoded enzyme called ___?_____ digests the bacterial cell wall and causes the cell to burst
lysozyme
why are steps 1,2,4,5 and 6 called the lytic cycle?
because they lead to cell lysis
phages must ___?___ their host cell to escape
lyse
latency is also called?
lysogeny
Bacteriophages that can follow lysogenic or lytic cycle are?
temperate phages
what is latency?
integration of genomes into a host chromosome
___?___ phages only have lytic cycles
virulent phages
what are episomes?
genetic elements
that replicate independently but occasionally integrate into host DNA
what are the two different mechanisms of latency in human viruses?
- Virus integrates into host genome and may remain dormant for long periods of time e.g. HIV
- Other viruses can exist as episomes e.g. Herpes simplex type I and II, varicella zoster (chicken
pox)
latent is the same thing as?
inactive or resting form
what are emerging viruses?
emerging viruses are ones that have arisen recently or have recently become more infectious, typically result from mutation in pre-existing viruses
list some examples of emerging viruses
coronavirus, new strains of influenza, zika virus, HIV/AIDS
what is a pandemic?
disease that occurs over a wide geographic area and affects a high proportion of the human population
what does H1N1 cause?
swine flu
what type of white blood cell does aids destroy?
helper T cell
what is regressive evolution in virus origin?
viruses are degenerate cells that have retained the minimal genetic information for replication
what are viroids?
they are composed solely of a single-stranded circular RNA molecule a few hundred nucleotides in length, infects plant cells and RNA genome does not code for protein
Prions
composed entirely of protein, converts normal protein to abnormal form
several types of neurodegenerative diseases of human and livestock
group of diseases called transmissible spongiform encephalopathies (TSE)
E.g. Scraple (disease of sheep and pigs characterized by intense itching followed by neurodegeneration), Mad cow disease (begins with changes in posture and temperament, followed by loss of coordination and neurodegeneration), Chronic wasting disease (a disease of seer and rocky mountain elk which symptom is weight loss over time, it is progressive and fatal)
