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Raj at 19:19, 3 January 2010

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<pre>The Origins of Genome Architecture
Micheal Lynch
</pre>
==History - 4.6 BYs ago==
# First origin of life is prior to 3.8 BYs
# RNA is primitive?
## DNA, though can self replicate, it is catalytically inert
## RNA is active
## RNA is proved to be selective of for variety of catalytic activities in various experiments
## As RNA can not replicate, primitive life forms existed as groups, involved in co-operative activities
## Cellular forms of life came into existence just few 100 MYs
## Prokaryotes - 0.5 - 1 BY
## Photosynthesis - 2.8 BY
## First algae - 2.1 BY
## Multicellular organisms - 0.5 BY - '''Cambrian Explosion'''
## Jawed Vertibrates and land plants - 0.4 BY
## Angiosperm - 0.14 BY
## Mammals - 0.1 BY
## Homo sepians - 0.002 BY
==DNA world==
# Initial DNA had U instead of T as evident from many viruses
# Why RNA based genomes were eradicated in the history?
## Probably DNA is more resistant to mutational vulnerability and stable relatively
# Viral Origin of DNA
## Most initial Virus had DNA based genome
## Being the DNA based genome, virus can easily get transferred into host RNA genomes
## They don't need to establish the additional defensive mechanisms as DNA itself was more tolerant to mutations
# Membranes - Early or Late?
## to the DNA world is not clear. But Koonin (That old man in SMBE) claims that cell membranes evolved independently subsequent to the establishment of DNA world

==3 domains of cellular life==
# Archea, Eubacteria, and Eukaryotes
## as evident form 16s subunit of rRNA (still rooting was a problem)
## duplicated genes can be used to root the tree
# ring of life
## Members of Archea and eubac. fused to form the eukaryotic domain
==Enkaryotes==
# Almost all eukaryotic genomes contains one or more minor genome aquired from Archea or eubacteria (mitochon., chloroplast)
# It is also clear that ancestral eukaryote could have had significant cell structure prior to origin of organelles
# Eukaryotes differs in
## genome size expansion
## chromosome linearity
## trans-splicing - operon
## exons-introns structure - splicing
## nuclear membrane
# Morphologically eukaryotes are classified as Unikonts and Bikonts
# '''BigBang'''
## Major lineages occurred between 10-100 MY, but there are discrepency
## varying information from differenty type of moleculr scale (protein coding sequence, fossil, etc)
Eukaryotic genome repaterning
## subac and archea - 100,00 species
## eukaryotes - 1,500,000 species
## New species
### geopgraphical isolation
### varying environments
### Intergenomic transfer of genes
### Reproductive incompatibility - facilitates
==Summary==
# RNA is first
# Protein synthesis started (RNA for information storage and protein for catalytic activity)
# Proteins assembled the DNA precursors
# Biotic pathway of construction of cell membrane appeared -> Cellular forms of life -> metabolic and mophological diversification

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The Origin of Eukaryotes - Revision history

Raj at 08:40, 23 June 2016

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Raj at 19:19, 3 January 2010