- Showed that mimicking prebiotic conditions in the lab could result in the production of the 20 most common amino acids.
- Proteins were originally thought to be the heritable information.
Peptide Nucleic Acid
- Possibly pre-RNA
- Similar to RNA
- Can be generated under ‘prebiotic conditions’
- Woese/Crick/Orgel proposed that RNA could catalyze reactions.
- RNAs can self-replicate, cut and elongate oligonucleotides
- present in many of the oldest (slowest evolving) and critical cellular processes
- transcription and translation, cofactors
- Can store and transmit information (and is subject to natural selection)
- High local concentrations speed assembly
- RNAs can polymerize in the presence of clay (montmorillonite)
Why RNA -> DNA?
- DNA allows for specialization in cells, DNA could store genetic info while RNA could be a cell messenger.
- DNA is more stable than RNA
- due to the deoxyribose sugar is less reactive
- double-strandedness (ds) shields information from unwanted interactions
- DNA replication has proof
- reading systems lacking in RNA replication
- ds also provides an inherent error-correction
- Higher stability = lower mutation rates = high fidelity = longer genes and genomes
- More information and more complexity
- Secretion systems
- Adhesins-proteins that recognize and bind specific substrates
- Motility-flagella, fimbrae (get where you need and attach)
- Toxins-endo/LPS, ecto
- antibiotic resistance
Virulence is not directly selected for, it's a by-product of selection on other traits.
Short sighted evolution
- A pathogen will experience many generations within a host that makes it well-adapted to its host before it can be transmitted.
- Traits for growth at the cost of transmissibility may rise to high frequency.
- Pathogenicity and transmissibility shape the alleles that rise to high frequency.
- Disease transmitted by physical contact have a reduced fitness.
Mutualisms are not important to the survival of either species, but engage in mutualism while the other species is around.