What is the
ORIGIN of LIFE...
a paradigm question for Cell & Molecular Biology...
the origins of the
Was it a
or an astrobiological
what was it?
Happens (a Panspermic event) or
Chemical Evolution & Emergence?
most experimental evidence favors a
chemical evolutionary origin of life...
self-assembly has lead to complex self-replicating chemical systems"
timeline: Earth forms
4.5 billion years ago,
4.0 bya -
asteroids bombard & sterilize planet's
4.0 bya - first
fossil evidence of microscopic life is present
Initial chemical events may have been
CARBON BASED MOLECULESwas
?) with simple reduced carbon gases...
ancient atmosphere (
carbon monoxide, carbon dioxide,
Let's look at experimental approaches &
research done to study Origins of Life*
experimental approaches are used in
Origin of Life
Lucentini, "Darkness before Dawn", The Scientist 17:(23) 28-29, 2003]
A) they were formed from a
chemically reactive soup... in early "oceans"
of primitive Earth.
Miller & Urey* ---> abiotic making of organics in lab experiments @ U.
> H2O, NH3, CH4,
& H2 make HCN &
of experimental organic syntheses
B) 1979 - Deep dwelling (ocean)
(deep sea volcanic plumes)
> vents* are full of organically rich molecules -->
tube worms* & bacteria ]
Speculation: chemosynthesis may have
originat in vents
origins for biomolecules...
Great 20th Century Discoveries ?
DEBRIS... space dust, meteorites, asteroids
deposited organics on newly formed planet Earth.
are mostly ice crystals on cores of silicates & carbon
contain about 10% CO, CO2, CH4, CH3OH, and NH3
Asteroids contain molecules as...
PAH], nucleobases, quinones,
COOH's, amines & amides
= some 70 amino acids, with
8 of common 20.
repeat of Miller-Urey famous experiments*
2nd) experimental approach:
built a MODEL MOLECULAR
Evolution of an RNA
in 1989 Sidney Altman
Tom Cech - received
for demonstrating that RNA molecules (RIBOZYMES)
have CATALYTIC ACTIVITY
RNA's catalyze hydrolysis & condensation rxs
of phosphodiester bonds,
RNA molecules able
to catalyze polymeric cleavage in a sequence-specific way.
RNA can be a
template and also
catalyze polymerization of like molecules,
molecules may have been the
No self-replicating RNA
molecules exists naturally today,
establish that it
is feasible, and that
RNA molecules can be selected for
via Darwinian evolutionary mechanisms (Natural
Robert Shapiro from NYU
suggests life began within a mixture of simple organic molecules,
catalyzed reaction cycles and an external source of available energy,i.e.,
a bunch of molecules that replicated each
thermodynamic theory for origin of life.
Origins of Life Prize -
chemically made artificial vesicle systems...
aggregates of prebiotic macromolecules that acquire a boundary to
an interior chemical environment distinct from "primordial soup"...
Sidney W. Fox
Univ of Miami
(1912 - 1998) - Director of NASA supported
Institute for Molecular Evolution
his laboratory conducted analyses of the
first moon rock
proteinoidsg from amino acid solutions... dropped on hot
lava rock,sand or clay.
proteinoid microspheres, and
or water filled vesicles (1-2um dia),
droplets form from polypeptides,
nucleic acidstough skin water molecules
held by hydrophobicity, possess osmotic capability
maybe with enzymatically active interior
- are osmotically active
with selective permeability
- have membrane potentials
- are microscopic spherical
vesicles that form when phospholipids are hydrated
- can engulf smaller proteinoids making more active ones
- in 2003 M. Hanczyc, S.Fujikawa, & J.Szostak
made liposomes that grow & divide via
if RNA present it was encapsulated [
a plausible route to 1st cells
approach) Synthetic Biology & Protocell Research...
a bottom-up approach:
assumes one can't truly understand what one can't build from scratch.
to assemble all the molecular components to be able to
synthetically form life
to understand why & how matter can self-organize... and become
is the construction of fully functional cells (or parts) from scratch.
the engineering of new genetic circuits, entire genomes, or
to make complex biological machines,
taking genetic elements to the level of
engineering a cell, and
altering gene content & arrangements to make novel designer genes.
i.e., the artificial creation of
viri, & cells that mimic, or surpass, natural systems.
- July 12 ,2002
Molecular Origin of Life Research or
from the University of New York at Stony Brook
the poliovirus' widely known
sequence to synthesize the virus from
shelf chemicals. They
followed a recipe they downloaded from
the internet and used gene sequences from a
mail-order supplier. The artificially constructed virus
appears identical to its natural counterpart; when injected
it into mice the animals were paralyzed and died.
Science 297, 1016-1018 (2002)
virus synthesized -
November 2003 :
Craig Venter and colleagues
created an artificial
by piecing together synthetic DNA ordered from a biotechnology
They used a technique called polymerase cycle assembly (PCA)
to link the strands of DNA together.
(Phi X-174 was 1st sequenced in 1978,
has 5,386 bp, 11 genes).
1918 Spanish Flu Virus is
October 2005 :
Jeffery K. Taubenberger, a
pathologist at the
Armed Forces Institute of Pathology and
his colleagues were able to piece together the
virus's genes from two unusual sources: 1)
lung tissue removed at autopsy from
a 21-year-old soldier &
2) the frozen body of an
Inuit woman who died of influenza in November 1918 &
was buried in the Alaskan
permafrost. These sources provided
pieces of viral RNA* that could be analysed
and sequenced. The
eight "RNA gene
segments" & by gene sequencing & PCR, they reassembled
of the 8 genes:
Hemagglutinin-A type 5 [H5] and
Neuraminidase type 1 [N1]
There are at least 16 different HA
antigens, which binds the
virus to the host cell. Hemagglutinin-A
surface glycoprotein that bind virus
to host cell.
is an surface antigenic glycoprotein enzyme
Nine neuraminidase subtypes
are known, which aid in the efficiency of virus release from
make up a subtype of human influenza virus A and the
avian influenza virus type A
B) synthetic biology...
a top-down-up approach:
KNOCK-OUT Cells... looking
for the minimalist essential genome required to make a cell...
J. Craig Venter,
a principle investigator (P.I.) of the
Human Genome Project
is trying to make
a new type of
bacterium using DNA
made in the lab from the sequenced genes of
gram-positive parasitic bacterium, whose primary
site may be the human urogenital tract that causes
582,970 base pairs, the smallest known
genome of any independently replicating
has a total of
encoding genes &
43 RNA genes).
> How many genes does it take to
make an organism? What is the minimum genes a
The scientists at
The Institute for Genomic Research (TIGR
this work by systematically destroying its genes
by mutating them with
microRNAs to see which ones are
essential to life & which
are dispensable]. Of the 482 protein-encoding genes, they concluded
265–350 of them are essential to life.
The next step is to artificially assemble
these 300+ genes to create a
- life from scratch?
So what did it take
to evolve a
as we know it today ?
these experiments are not yet done...
evolution of the eucarya
was single most important
step in evolution
forms & was a key step that lead to plant &
cell membrane encapsulates genetic DNA...
development of nucleus
greatest evolutionary invention - it
internalized the genome
2. loss of a rigid cell wall...
cells developed ability of
phagocytosis - allowed engulfing of foods
also allowed cells to clump together -->
multi-cellularity --> tissues
3. evolve a selectively permeable membrane...
allows uptake gases & nutrients & exchange with environment
4. evolve a cytoskeleton...
framework- allowed cell to grow larger, move, &
eucarya are 10x
larger that bacteria
5. evolve aerobic respiration...
more efficient energy transformation
6. develop various organelles...
a sub-cell part
that catalyzes a specific metabolic function
7. development of sexual cell cycles...
method to shuffle genes along chromosomes favored cellular evolution