Transcript Ddddddd

ASTR/GEOL-2040: Search for life
in the Universe: Lecture 5
• Murchison meteorite
• Comp with Miller/Urey
• Artificial life
Make sure to pick up model solutions
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Darwinian evolution: testable theory
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Ammonia: weakly polar
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Last time
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Carbon from astrophysics (fusion)
Protostellar disk forms rapidly
Reducing H2, H2O, NH3, CH4
Discharges
Steam
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Recall problems with Miller/Urey?
• Now know: Methan & ammonia unlikely
– Experiment went out of fashion
– CO2 and N2 would have been abundant
• Miller forgot one of his vials: H2S
– Relevant to volcanos, recovered in 2007
– 23 amino acids!
• Main flaw: mass equilibrium: reactor design
Lon: p.215, BS: 207
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Shock waves + biology ??
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Reducing atmosphere:
H2, H2O, NH3, CH4,
Discharges
Steam
Can you think of examples?
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Shock
waves
?
Perhaps
not stupid
at all!
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LHB=
• late heavy
bombardment
• Much later than
moon-forming
impact (20Myr?)
– Moon craters
• Geological eons
> eras > periods
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Meteorites: different types
• Stony:
– Chondrites: 86%
• Ordinary (80% of those)
• Carbonateous (5% of those)
• ....
– Achondrites:8%
• Iron: 6%
Chelyabinsk
1500 people injured!
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Meteorites: different types
• Stony:
– Chondrites: 86%
• Ordinary (80% of those)
• Carbonateous (5% of those)
• ....
– Achondrites:8%
• Iron: 6%
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Murchison meteorite
• September 28, 1969, 10:58 am, Melbourne
– Observed as fireball, w/ smoke for 30s
– Broke up into pieces, altogether >100kg
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Carbonaceous chondrite
Smelly when found
Analyzed like moon rocks
>15 amino acids, etc
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Amino acids in Muchison
• September 28, 1969, 10:58 am, Melbourne
– Observed as fireball, w/ smoke for 30s
D- and L-forms?
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What we did last time
• The
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Difference left/right?
Looks the same
in the mirror
 achiral
Looks different
in the mirror  chiral
D form: dextrorotary
L form: levorotary
• D form  sense of rotation right-handed
• L form  ”
”
”
left-handed
Left-handed
Right-handed
• Miller/Urey
– Left/right equal
• Life (amino acids):
– left-handed
• Sugars (nucleotides)
– Right-handed
Comparison
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Reducing atmosphere:
x
H2, Hx2O, NH3, CH4,
not used
Discharges
x
In life
Steam
x
x
x
x
x
x
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What we did last time
• The
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Organics in Muchison & Life
• Long polymers absent (single sugars, no proteins)
• No nucleotide nor nucleic acids
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Monomers of building blocks
…what is not found
A. amino acids
B. sugars
C. nucleotides
D. lipids
E. none (all are found)
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Organics in Muchison & Life
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x
x
x
• Long polymers absent (single sugars, no proteins)
• No nucleotide nor nucleic acids
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Purines & pyrimidines
Purines
Pyrimidines
G (guanine)
A (adenine)
Xanthine
hypoxanthine
(U Uracil)
(4-hydroxypyrimidine)
• Bases not used in terrestrial life
• Not all of the bases of terrestrial life found
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The importance of the
Miller/Urey experiment is
A. It proved beyond doubt that life could
have arisen natually on Earth;
B. it showed that natural chemical reactions
can produce building blocks for life;
C. it showed that clay can catalyze the
production of RNA.
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Check by elimination
• proved beyond doubt that life could have
arisen natually on Earth?
– There was no life in this experiment
– Just amino acids and other organics
• showed that clay can catalyze the
production of RNA?
– Clays were not involved here
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The importance of the
Miller/Urey experiment is
A. It proved beyond doubt that life could
have arisen natually on Earth;
B. it showed that natural chemical reactions
can produce building blocks for life;
C. it showed that clay can catalyze the
production of RNA.
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What this really tells us:
• Making many of the building blocks is easy
– delived from space
– early atmospheric ?reducing conditions
– Deep-sea vents (discussed later)
– Heat & pressure from impacts
• Many possibilities  no conclusive answ.
• Unclear how to assemble them
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Guidance from “artificial life”
• Not computer life (HW1), but microbial
– Not Frankenstein  practical applications
• Engineering, start from existing organisms
• Making life from raw ingredients
– Synthetic biology
• Safety issues
BS: 233-238
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JCVI-syn1.0  3.0
• Genome modified from existing one
– Minimalistic genome
– Quasiessential genes,  robust growth
– But otherwise synthesized from scratch
• Inserted into cell body of another bacterium
– Its own genome removed
• Modified bacterium boots up/comes to life
– Naturally reproduces/evolves
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Practical applications?
• Bacteria inhale/exhale/eat/excrete
• Are small: target certain body parts
• Can they solve some of the outstanding
problems of our time?
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Practical applications?
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...............
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Think also of biologically engineered life
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Practical applications?
• CO2 sequestration
– Converting CO2 CH4
– CH4 fuel (CO2 neutral)
• Cleaning up oil spills
– Toxic waste removal
• Medical: e.g. attack cancer cells
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JCVI-syn1.0  3.0
Science 351, 1414-U73 (2016)
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1 bp = one base pair
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1 bp: A, T, G, C
1 bit: 0, 1
1 byte: a, b, c, A
1 byte = 8 bit
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How much is 531 kbp?
A.
B.
C.
D.
E.
130 kbyte
1.3 Mbyte
13 Mbyte
130 Mbyte
1.3 Gbyte
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1 base pair?
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1 bit: 0, 1
2 bit: 00, 01, 10, 11
1 bp: A, T, G, C
1 byte = 8 bit = 4 bp
 1 pb = 2 bit
 divide by 4
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How much is 531 kbp?
A.
B.
C.
D.
E.
130 kbyte
1.3 Mbyte
13 Mbyte
130 Mbyte
1.3 Gbyte
because:
531/4 ~ 130
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Human genome: 2.9 Gbp
A.
B.
C.
D.
E.
72.5 Mbyte
725 Mbyte
7.25 Gbyte
72.5 Gbyte
725 Gbyte
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Human genome: 2.9 Gbp
A.
B.
C.
D.
E.
72.5 Mbyte
725 Mbyte
7.25 Gbyte
72.5 Gbyte
725 Gbyte
because:
2900/4 ~ 725
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Venter
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Life from raw ingredients
• Also called: A-Life or ALife
– Szostak & Cech (Nobel Prize 2009)
– Org soup + clay surface  RNA strands
• One of those might, by chance, reproduce
– Fastest, most accurate  survive
• RNA-based cells
– Mix RNA strands with fatty acids  cells
– Fast-forward chem evol 1012 copies, etc
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Life fro
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Should we create A-life?
• Advantages: fuel, cancer, waste, etc...
• Dangers: deadly organisms w/o nat enemies
– Biowarfare, hard-to-foresee risks
• Engineer  cannot survive in the wild
– Rebuild code  nonnatural amino acids
• Hope: learn more about origin of life
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Websites for papers
• Web of Science
• See the links under my home page
– http://lcd-www.colorado.edu/~axbr9098/teach/ASTR_2040/
• Web of Science, Google Scholar, ADS
• See also link to D2L
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What we talked about
• Meteorites can deliver amino acids and
some of the bases of DNA
• Similar to Miller/Urey experiment
• Artificial life (A-Life)
• How to find in-depth reading material
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Next time
• Delivery of water & carbon by comets
• Panspermia (delivery of seeds for life)
• Reading:
– RGS pp. 23-34
– Lon pp. 383-384, 176, 112
– BS pp. 121-127, 144-146
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