Evolutionary Thinking & HIV/AIDS Crisis Flashcards
Why do moth ear mites only affect one year
parasites evolved to infect one ear so that the moth can still hear the bat
Why is bat echolocation so loud
signal must reach prey and then bounce back to bat (within 1-2 ms)
What does fossil records indicate about flight and echolocation
flight evolved before echolocation
What are some major epidemics in human history
influenza, “black death”, new world smallpox, HIV/AIDS
How many AIDS related deaths have there been since 1981
30 million
As of 2010, how many people worldwide are living with HIV/AIDS
34 million people
What percentage of deaths has been from HIV
4.9%- more than TB, malaria, car accidents, homicides, and wars
Where is the HIV prevalence the highest
in sub-Saharan Africa (7.2% adults, >20% in some countries)
What is the life expectancy in some sub-Saharan countries
<50
What is the prevalence in western Europe, Canada, and USA?
western Europe (0.3%) Canada (0.3%) USA (0.6%)
How is transmission different in sub-Saharan Africa, China, and US/western Europe
sub-Saharan- heterosexual sex, China- intravenous drug use, blood donors, heterosexual sex, US/western Europe- homosexual sex, needle sharing, heterosexual sex
What is HIV and what does it attack
it is a retrovirus, an intracellular parasite that needs host cells to reproduce. It attacks cells of the immune system, especially helper T cells. Produces DNA that is inserted into hosts genome. Uses host’s polymerases ribosomes and tRNAs to reproduce
What are AIDS deaths due to and why
secondary infections, depletion of T cells exposes body to pathogens
What is AZT and why did AZT fail
a drug intended to inhibit viral enzyme reverse transcriptase. AZT stops reverse transcription by lacking an hydroxyl group to which next nucleotide would attach- effective early on. By 1989 patients stopped responding
Why did AZT form a resistance
reverse transcriptase is error prone- HIV has no error-correction, over half of transcripts have an error, HIV has highest mutation rate of any organism, Thousands of generations during course of infection producing many variants of reverse transcriptase
What are the four necessary and sufficient conditions for evolution by natural selection
- variation 2. heritability 3. genotype produces phenotype with fitness consequences 4. differential production of offspring
How does HIV use variation to its advantage
transcription errors produce mutations in reverse transcriptase genes, produces reverse transcriptase that varies in resistance to AZT
How does HIV use heritability to its advantage
mutant virions pass their reverse transcriptase genes on to their off-spring
How does HIV use genotype producing phenotype with fitness consequences to its advantage
some mutations produce reverse transcriptase that perform better in the presence of AZT
How does HIV use differential production of offspring to its advantage
virions that pass on genes for AZT-resistance produce more offspring that survive and reproduce in host. Genes with resistance increase within population
In drug therapy, what does protease inhibitors do
prevent HIV from producing final viral proteins from precursor proteins
In drug therapy, what do fusion inhibitors do
prevent HIV from entering the cell
In drug therapy, what does integrate inhibitors do
prevent HIV from inserting HIV DNA into host’s genes
What is HAART
Highly-Active AntiRetroviral Treatments
How does HAART work
makes evolution of drug-resistance by natural selection on virus more difficult, drug cocktails require multiple mutations simultaneously with a single viral particle
What are the effects of HIV on the hosts immune system
Rapid epitope evolution allows high level of replication, exhausting naive and memory T-cells. Viral population evolves toward even more aggressive replication. HIV can evolve to infect naive T-cells
Is HIV fatal because of “short-sighted” evolution
virions are thoughtless, molecular machines. Evolve with no care for the future. High replication rates may also favor transmission, despite being fatal to hosts.
Selection affects HIV lethality in two ways:
- within the host: selection to defeat hosts defenses factors high replication rates, more replication means more opportunities for favorable mutations. 2. between hosts: selection favors high viral loads, higher loads= more effective transmission.
HIV-resistance patients often have a mutant form of?
CCR5 co-receptor (∆32)
What is CCR5 gene associated with
resistance to SIV in primate species
Where did HIV-1 come from
jumped from chimps from the exposure while butchering “bush meat”
