Lecture 9 - Origins and Evolution of Life Flashcards
1
Q
significance of LUCA
A
starting point for evolution of extant lineages
2
Q
views on domain relationships
A
- three-domain tree of life
- two-domain tree of life
3
Q
application of parsimony
A
- assume a given phylogenetic tree topology
- assume a given distribution of traits among taxa
- assume the scenario with the least number of evolutionary events is correct
- search in alternatives for scenario that minimized evolutionary events
4
Q
HGT spread
A
- microbes readily take up DNA but foreign DNA rarely spreads into population
- core portions do not undergo HGT
5
Q
core genes
A
determined to reconstruct phylogeny
6
Q
two-domain tree of life
A
no size constraint in LUCA results in all genes present in at least one bacterium and archaeon
7
Q
reconstructing a phylogeny
A
- predict protein sequences
- cluster based on % similarities
- ML phylogenetic analysis
- maximum likelihood phylogenetic trees
8
Q
criteria to identify LUCA proteins
A
- orthologues present in at least 2 phyla of both archaea and bacteria
- tree topology is consistent with monophyly of bacterial and arachaeal sequences
9
Q
LUCA
A
- small genome
- anaerobic
- lived in hydrothermal setting
- nitrogen-fixer
- acetogenic and methanogenic roots
- universal genetic code
- free-living bacterium
- possibly a thermophile
10
Q
Pelagibacter ubique
A
- small genome
- member of SAR11 clade
- aerobic
- free-living
- chemoheterotrophic
- phototrophic
11
Q
reverse gyrase
A
- supercoils DNA
- only present in hyperthermophiles
12
Q
LUCA membrane
A
still debated if it was monoderm or diderm as these characteristics are polyphyletic
