Flashcards in Lecture 20 - Viruses pt 2 Deck (25)
What are 3 Prokaryotic defenses?
1. evolution of host cell surface receptors
2. restriction enzymes
3. CRISPR-Cas9 immune system
What is the cycle of evolution between prokaryotes and viruses?
-host evolves to prevent attaching
-viruses evolve to attach anyway
What are restriction enzymes?
enzymes that cut the genome at a particular spot in the sequence
Why are restriction enzymes used against viruses?
cuts the viral sequence into 2
How do restriction enzymes not eat its own genome?
-methylates its own DNA
What does a phage do in response to the host methylating?
phage methylates its own restriction sites
What does the host do in response to the virus methylating?
host detects and cuts methylated sites into phage via MDS
How does the phage protect its methylated sites?
What is CRISPR-Cas9?
specific gene editing system
What are the 4 steps to CRISPR?
1. virus invades bacterial cell
2. new spacer derived from virus, integrated into CRISPR
3. CRISPR RNA formed
4. CRISPR RNA guides molecular machinery to target + destroy viral genome
What are 4 defenses Humans have against viruses?
2. immune system
4. antiviral drugs
viruses are a dominant driver of _____ ______ in mammals
What is a vaccine?
-harmless variant/derivative of a pathogen
-stimulates the immune system to mount defenses
What is herd immunity?
-if most individuals in herd are vaccinated
-can prevent spread of virus
How does the immune system work?
-macrophages swallow up germ (leave antigen)
-evoke antibody response
Is there a link between vaccines and autism?
Why do vaccines need to be continually updated?
-pathogens change (molecules on surface change)
What are 2 reasons that pathogens change?
1. antigenic drift
2. antigenic shift
What is antigenic drift?
due to mutations in genes encoding them
What is antigenic shift?
due to recombination of genes of existing pathogens
What are emerging viruses?
viruses that suddenly become apparent
What are 3 causes of emerging viruses?
1. mutation of existing viruses (seasonal flu)
2. spread from isolated human populations (AIDS)
3. spread from other animals (HINI)
What is an antiviral?
something you take after you are infected
What do antibiotics target?
-bacterial cell walls