Lecture 14 Evolution and Human Health

Cholera Caused By

-cholera caused by infection of intestine with bacteria

Germ Theory of Disease

-microorganisms can cause disease in people and animals

Tuberculosis Spread and Infection

-infection of lungs

-spreads via droplets

Why did death rates for tuberculosis decrease?

-discovery of antibiotics

What can analysis of framework be helpful with diseases?

-Analysis frameworks like phylogenetics can inform how diseases are related in time and space.

Evolving Pathogens

-pathogens consume the hosts tissues and convert them

-hosts slow damage by killing pathogens

Influenza A Virus

-8 RNA strands

-main coat protein called hemagglutinin

Hemagglutinin

-initiates infection to sialic acid on surface of host cell

-primary is primary protein recognized, attacked, and remembered by host immune system

Flu Virus Evolution Study

-consistent with neutral theory: silent substitutions out number (non-synonymous) mutations

Hemagglutinin Sites Under Selection

-18 sites under strong positive selection in flu virus

-human immune system in agent of selection

How do pandemic strength flu strains Emerge?

-flu strain could alter hemagglutinin protein so it’s not recognized by human immune systems, BY FINDING NEW COPY OF HEMAGGLUTININ

nucleoproteins

-main gebes responsible for host-specifictiy, controls virus ability to infect host cells

1968 pandemic strain

-H3 got into pigs via birds

Antibiotic Resistance

-antibiotics kill bacteria, the bacteria can aquire more bacterial plasmids or lose enzymes antibiotics need to work

Evidence for evolution of antibiotic resistance

-populations of bacteria raised as a response to treatments

ex) penicillin resistance

Costs of Antibiotic Resistance

-maintaining new plasmids

-losing functions

-antibiotic resistant bacteria less fit than non-resistant when antibiotics not present

3 Hypothesis of Varying Virulence in Human Pathogens

1) virulence could be accidental by-product of selection in other traits

2) shortsighted evolution hypothesis- pathogens may experience new gens of evolution by natural selection before moving to new hosts.

3)trade-off hypothesis- natural selection favors pathogens with balance on costs and benefits to hosts.

Virulence Levels

Directly transmitted diseases have lower virulence than vector-borne diseases.

-higher freq. of waterborne transmission more virulent

Cancer Progression In evolution: Association, mutations

-liver cancer associated w/ hep. B infection

-before divergence of tumor, the cells near liver cells had many more mutations

6 Hallmarks of Cancer

1. Self-sufficiency of cells in signals controlling growth
2. Loss of sensitivity to antigrowth signals
3. Evasion of apoptosis via mutation or loss of gatekeeper genes
4. Development of limitless replicative potential, usually via the expression of
telomerase
5. Sustained angiogenesis, whereby the blood supply to a tumor is augmented
6. Tissue invasion and metastasis

Predation: Cancer

• immune system attack on foreign cells

• selects for cancer cells that can escape immune system

Competition: Cancer

• cells exist in cellular niche

• growth is limited by lack of resources

• competition between cancer cells maintains diversity

Variation: Cancer

• genetic variation is material for selection

• cancers develop genomic instability which increases variation

Genetic Drift: Cancer

-tumor suppressor genes could be randomly lost

Sexual Selection: Cancer

-cancer takes advantage of genes involved in spermatogenesis