Lec1 the Role of Evolution

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agvargasagvargas01.VI.200601.VI.2006

The Role of Evolution and the Moleculesof Life

Evolution is the theory that all living thingsEvolution is the theory that all living things

have changed in response to environmentalhave changed in response to environmental

conditions by the natural selection of randomlyconditions by the natural selection of randomlyoccurring mutations, developing from the simplestoccurring mutations, developing from the simplest

forms to complex forms hich are more prolificforms to complex forms hich are more prolific

and stronger, due to their better adaptation toand stronger, due to their better adaptation to

their environment.their environment.

!harles "arin!harles "arin provided this insight thatprovided this insight thatestablishes a great chain connecting the distantestablishes a great chain connecting the distant

past to the present.past to the present.

#t the molecular level, evolution is the history#t the molecular level, evolution is the history

of the emergence of more complex biomoleculesof the emergence of more complex biomolecules

from simpler organic monomeric units or evenfrom simpler organic monomeric units or evenfrom inorganic counterparts.from inorganic counterparts.

http://www2.lucidcafe.com/lucidcafe/library/96feb/darwin.htmlhttp://www2.lucidcafe.com/lucidcafe/library/96feb/darwin.htmlhttp://www2.lucidcafe.com/lucidcafe/library/96feb/darwin.html


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$he ell %non$he ell %non &iller'(rey experiment &iller'(rey experiment

shoed that simple components can reactshoed that simple components can react

abiotically )or in the absence of life* to giveabiotically )or in the absence of life* to give

rise to biologically important compounds +rise to biologically important compounds +

such as components of proteins and nucleicsuch as components of proteins and nucleic

acids.acids.

par%'dischargeapparatus type used inthe &iller and (reyexperiment demonstratingthe formation of organiccompounds in abiotic,primitive atmosphericconditions. -ater isheated in a closed systemcontaining /, !/, and

/2. #n electric discharge

is passed through themixture of gasessimulating lightning. #fterseveral days, organicmolecules including aminoacids ere among theproducts collected.

click to

see bigger picture

http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/miller.htmlhttp://www.chem.duke.edu/~jds/cruise_chem/Exobiology/miller.htmlhttp://www.chem.duke.edu/~jds/cruise_chem/Exobiology/miller.html


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#fter the spontaneous synthesis of#fter the spontaneous synthesis of

organic molecules, the next step in evolutionorganic molecules, the next step in evolution

as the formation of macromolecules. (nderas the formation of macromolecules. (nder

prebiotic conditions, macromolecules areprebiotic conditions, macromolecules are

formed spontaneously from monomericformed spontaneously from monomeric

building bloc%s as shon belo.building bloc%s as shon belo.

Figure from Lehninger,

Albert et. al. 1993.

Principles of Biochemistry

2 nd ed. orth Publishers,

!e" #or$.


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rom macromolecules come supramolecularrom macromolecules come supramolecular

complexes hich no become integral partscomplexes hich no become integral parts

and components of living cells.and components of living cells.

Figure from Lehninger,

Albert et. al. 1993.

Principles of Biochemistry

2 nd ed. orth Publishers,

!e" #or$.


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3ne of the important molecules of life is3ne of the important molecules of life is

hat e %no as genes + but are actuallyhat e %no as genes + but are actually

chemically,chemically, deoxyribonucleic acids (DNA)deoxyribonucleic acids (DNA)

++ that define biological structure and maintainthat define biological structure and maintain

cellular integrity. $hese genes encodecellular integrity. $hese genes encode

proteinsproteins that ma%e up cellular structuresthat ma%e up cellular structures

and carry out many activities in the cell,and carry out many activities in the cell,

particularly catalytic activity, that increasesparticularly catalytic activity, that increases

rates of cellular reactions producing largerates of cellular reactions producing large

numbers of complex molecules. $henumbers of complex molecules. $he

4 4decoding5 or expression of coded geneticdecoding5 or expression of coded genetic

info in "# into proteins is made possible byinfo in "# into proteins is made possible by

another molecule + theanother molecule + the ribonucleic acidsribonucleic acids

(RNA)(RNA)..


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$his trio of macromolecules + "#, #$his trio of macromolecules + "#, #andand

proteins + is present in all cells. $he restproteins + is present in all cells. $he restareare

polysaccharides, ater, inorganic ions and apolysaccharides, ater, inorganic ions and a

large array of small organic molecules.large array of small organic molecules.


DNA

RNA

Protein


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$he central dogma of molecular biology$he central dogma of molecular biology

illustrated in the figure belo shos theillustrated in the figure belo shos the

organi7ing principle in the flo of geneticorgani7ing principle in the flo of genetic

information8 "# to # to protein.information8 "# to # to protein.

Sources of Figures:

%ampbell, &ary '. and (ha"n ). Farrell. 2**+. Biochemistry th ed. -homson

Broo$s%ole, Belmont, %A.

Lehninger, Albert et. al.1993. Principles of Biochemistry 2 nd ed. orth Publishers, !e"

#or$.


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3f the macromolecules in present'day3f the macromolecules in present'day

cells, only the nucleic acids are capable ofcells, only the nucleic acids are capable of

directing their on self'replication.directing their on self'replication.

ucleic acids can serve as templates forucleic acids can serve as templates fortheir on synthesis as a result of specifictheir on synthesis as a result of specific

base pairing beteen complementarybase pairing beteen complementary

nucleotides.nucleotides.

4 4# critical step in understanding# critical step in understanding

molecular evolution as thus reached in themolecular evolution as thus reached in the

early 19:0s, hen it as discovered in theearly 19:0s, hen it as discovered in the

laboratories oflaboratories of id #ltman id #ltman and $om !echand $om !ech

that # is capable of cataly7ing a numberthat # is capable of cataly7ing a number

of chemical reactions, including theof chemical reactions, including thepolymeri7ation of nucleotides. # is thuspolymeri7ation of nucleotides. # is thus

uni;uely able both to serve as a templateuni;uely able both to serve as a template

for and to cataly7e its on replication.for and to cataly7e its on replication.

%ampbell, &ary '. and (ha"n

). Farrell. 2**+. Biochemistry

th ed. -homson Broo$s%ole,

Belmont, %A.

http://nobelprize.org/chemistry/laureates/1989/altman-autobio.htmlhttp://nobelprize.org/chemistry/laureates/1989/altman-autobio.htmlhttp://nobelprize.org/chemistry/laureates/1989/altman-autobio.html


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!onse;uently, # is generally believed!onse;uently, # is generally believed

to have been the initial genetic system, andto have been the initial genetic system, and

an early stage of chemical evolution is thoughtan early stage of chemical evolution is thought

to have been based on self'replicating #to have been based on self'replicating #

molecules a period of evolution %non as themolecules a period of evolution %non as the

RNA worldRNA world..

3rdered interactions beteen # and3rdered interactions beteen # and

amino acids then evolved into the present'dayamino acids then evolved into the present'daygenetic code, and "# eventually replaced #genetic code, and "# eventually replaced #

as the genetic material.5 as the genetic material.5

/(ource0/(ource0 %ooper, . &. 2***. -he%ooper, . &. 2***. -he

%ell 0 A &olecular Approach. 2 %ell 0 A &olecular Approach. 2 nd nd ed.ed.

(inauer Associates, nc., (underland, &A.(inauer Associates, nc., (underland, &A.

Link to RNA-world

Hypothesis


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agvargasagvargas01.VI.200601.VI.2006Figures from %ampbell, &ary '. and (ha"n ). Farrell. 2**+.Biochemistry th ed. -homson Broo$s%ole, Belmont, %A.

The following gures show the stages in theevolution of a system of self-replicating RNAmolecules. At each stage more comple!ity appearsin the group of RNAs leading eventually to the

synthesis of proteins as more e"ective catalysts.


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Lec1 the Role of Evolution