Bio Ch 20 Flashcards
Virus
associated with a number of plant, animal, and human diseases; biological enigma
Capsid
all viruses have; composed of protein subunits and an inner core of nucleic acid (either DNA or RNA, but not both)
Obligate intracellular parasites
viruses; can’t reproduce outside a living cell
Bacteriophages (phages)
viruses that parasitize bacteria
Lytic Cycle
5 stages: attachment, penetration, biosynthesis, maturation, & release
Lysogenic Cycle
infecting phage does not immediately proliferate, but may do so sometime in the future; in the meantime, the phage is latent (not actively replicating)
Prophage
while latent, the viral DNA is called this
Lysogenic Cells
prophage is replicated along with the host DNA and all subsequent cells (called this) carry a copy of the prophage genome
Retroviruses
animal viruses with an RNA genome that is converted into DNA within the host cell by a special enzyme called reverse transcriptase
Reverse Transcriptase
special enzyme that converts an RNA genome into DNA within a host cell
Emerging Viruses
new or previously uncommon illnesses caused by viruses that are able to infect large numbers of humans; AIDS, West Nile encephalitis, hantavirus pulmonary syndrome (HPS), severe acute respiratory syndrome (SARS), Ebola hemorrhagic fever, and avian influenza (bird flu)
Viroids
naked strands of RNA (not covered by a capsid); causes crop diseases (potatoes, coconuts, citrus)
Prions
proteinaceous infectious particles; cause a number of fatal brain diseases known as transmissible spongiform encephalopathies (TSE’s); proteins that normally exist in an animal, but have a different conformation/structure; cause infection by interacting with a normal protein and altering its structure
Neurogenerative Diseases
TSE’s; those that destroy nerve tissue in the brain; ex = mad cow disease
Prokaryotes
bacteria & archaea; fully functioning, living, single-celled organisms
Flagella
some prokaryotes move by means of this; bacterial type has a filament composed of strands of the protein flagellin wound in a helix
Fimbriae
short bristlelike fibers extending from the surface of many prokaryotes
Nucleoid
dense area in a prokaryote where a single chromosome consisting of a strand of circular DNA is found