Evolutionary Thinking & HIV/AIDS Crisis

Question 1

Why do moth ear mites only affect one year

Answer 1

parasites evolved to infect one ear so that the moth can still hear the bat

Question 2

Why is bat echolocation so loud

Answer 2

signal must reach prey and then bounce back to bat (within 1-2 ms)

Question 3

What does fossil records indicate about flight and echolocation

Answer 3

flight evolved before echolocation

Question 4

What are some major epidemics in human history

Answer 4

influenza, “black death”, new world smallpox, HIV/AIDS

Question 5

How many AIDS related deaths have there been since 1981

Answer 5

30 million

Question 6

As of 2010, how many people worldwide are living with HIV/AIDS

Answer 6

34 million people

Question 7

What percentage of deaths has been from HIV

Answer 7

4.9%- more than TB, malaria, car accidents, homicides, and wars

Question 8

Where is the HIV prevalence the highest

Answer 8

in sub-Saharan Africa (7.2% adults, >20% in some countries)

Question 9

What is the life expectancy in some sub-Saharan countries

Answer 9

<50

Question 10

What is the prevalence in western Europe, Canada, and USA?

Answer 10

western Europe (0.3%) Canada (0.3%) USA (0.6%)

Question 11

How is transmission different in sub-Saharan Africa, China, and US/western Europe

Answer 11

sub-Saharan- heterosexual sex, China- intravenous drug use, blood donors, heterosexual sex, US/western Europe- homosexual sex, needle sharing, heterosexual sex

Question 12

What is HIV and what does it attack

Answer 12

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

Question 13

What are AIDS deaths due to and why

Answer 13

secondary infections, depletion of T cells exposes body to pathogens

Question 14

What is AZT and why did AZT fail

Answer 14

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

Question 15

Why did AZT form a resistance

Answer 15

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

Question 16

What are the four necessary and sufficient conditions for evolution by natural selection

Answer 16

1. variation 2. heritability 3. genotype produces phenotype with fitness consequences 4. differential production of offspring

Question 17

How does HIV use variation to its advantage

Answer 17

transcription errors produce mutations in reverse transcriptase genes, produces reverse transcriptase that varies in resistance to AZT

Question 18

How does HIV use heritability to its advantage

Answer 18

mutant virions pass their reverse transcriptase genes on to their off-spring

Question 19

How does HIV use genotype producing phenotype with fitness consequences to its advantage

Answer 19

some mutations produce reverse transcriptase that perform better in the presence of AZT

Question 20

How does HIV use differential production of offspring to its advantage

Answer 20

virions that pass on genes for AZT-resistance produce more offspring that survive and reproduce in host. Genes with resistance increase within population

Question 21

In drug therapy, what does protease inhibitors do

Answer 21

prevent HIV from producing final viral proteins from precursor proteins

Question 22

In drug therapy, what do fusion inhibitors do

Answer 22

prevent HIV from entering the cell

Question 23

In drug therapy, what does integrate inhibitors do

Answer 23

prevent HIV from inserting HIV DNA into host’s genes

Question 24

What is HAART

Answer 24

Highly-Active AntiRetroviral Treatments

Question 25

How does HAART work

Answer 25

makes evolution of drug-resistance by natural selection on virus more difficult, drug cocktails require multiple mutations simultaneously with a single viral particle

Question 26

What are the effects of HIV on the hosts immune system

Answer 26

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

Question 27

Is HIV fatal because of “short-sighted” evolution

Answer 27

virions are thoughtless, molecular machines. Evolve with no care for the future. High replication rates may also favor transmission, despite being fatal to hosts.

Question 28

Selection affects HIV lethality in two ways:

Answer 28

1. 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.

Question 29

HIV-resistance patients often have a mutant form of?

Answer 29

CCR5 co-receptor (∆32)

Question 30

What is CCR5 gene associated with

Answer 30

resistance to SIV in primate species

Question 31

Where did HIV-1 come from

Answer 31

jumped from chimps from the exposure while butchering “bush meat”