Bio Class 3: Microbiology Flashcards
- Prions are misfolded protein molecules which propagate by transmitting an misfolded protein state. if a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, misfolded prion form; the prion acts as a template to guide the misfolding of more proteins into prion form. These newly formed prions can then go on to convert more proteins themselves. Bovine spongiform encephalopathy or “mad cow disease” is caused by prions. Which level of protein structure was NOT affected in Mad Cow Disease? A. primary B. Secondary C. Tertiary D. Quarternary
A. primary
T/F: You can have an enveloped bacteriophage
True, but they so not infect bacteria ??
(cf pg156 bio question)
why does the bacteriaphage need to enter by penetration rather than endocytosis?
because bacteria have a cell wall made up of peptidoglycan that creates a tough barrier. Energy from ATP contracts the shaft/sheath of bacteriophage, which can overcome the barrier
T/F: only animal viruses are enveloped
true
(but not all animal viruses are enveloped)
phage penetration is also called eclipse because
the genome is being injected into the bacteria, rending the medium non-infectious (eclipse period is a period of non-infectivity)
T/F: a bacteriophage genome can enter either the lytic or lysogenic cycle.
true
What happens in the lytic cycle of a phage
The lytic cycle is infectious cycle with the following steps:
- rapid transcription and translation of virus genome using host machinary, one of which is hydrolase (early gene)
- hydrolase degrades host genome
- Virus uses the dNTPs from host to make several copies of its genome
- late gene lysozyme is produced, which degrades the bacterial cell wall inducing water to flow in and bursts the cell fully, lysing it (mnemonic: lyse-lytic)
What occurs in the lysogenic cycle (for phages)?
Non-immediately-infectious cycle
- phage genome incorporates into host genome via integration → called prophage and host called lysogen
* phage repressor proteins that bind to phage promotors block transcription of phage genes during the dormancy - everytime the host cell replicates, the viral genome is replicated too
- eventually, the phage is activated and removes itself from host genome in a process called excision
- phage enters lytic cycle
what is tranduction and how does it occur?
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector.
It happens as a possible outcome of the lysogenic cycle. The viral genome may take a small part of host genome with it when its excised at the end of lysogenic cycle.
If that phage then infects a new bacteria and induces lysogenic cycle, the stolen segment of bacterial DNA will be incorporated into new bacterial DNA
bacteriophage is to animal virus
as
lytic cycle is to ______
______ is to provirus
productive cycle
prophage
(+) RNA viruses must encode a RNA dependent RNA pol and must/does not have to carry it
(+) RNA viruses must encode a RNA dependent RNA pol and does not have to carry it (because plus strands can be immediately transcribed)
(-) RNA viruses must encode a RNA dependent RNA pol and must/does not have to carry it
(-) RNA viruses must encode a RNA dependent RNA pol and must carry it
because a positive sense strand has to be made first before any transcription can happen
retroviruses use __________ to reverse transcribe DNA from RNA
RNA dependent DNA polymerase
(aka reverse transcriptase)
^encoded by virus
which type of virus uses host cell RNA pol?
one of the dsDNA (adenovirus)
a hallmark of prion disease is
long incubation periods
plasmids are
cicular extra-chromosomal genetic elements. but also circular. Called the fertility factor because it is what causes genetic transfer between bacterium. Denoted by F+
