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Introduction to
Molecular Biology
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Content
Cells and organisms
Molecules of life (Biomolecules)
Central dogma of molecular biology
Genes and gene epression
@: Most pictures have been freely obtained from:
http://www.accessexcellence.org/
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Cells & organisms
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Cells and organisms
#rganisms
$nicellular% #ne single cell (or simpler)
&rc'aea
(ro)aryotes% Bacteria* +east
Eu)aryote% (roto,oos
(luricellular% Eu)aryote cells
Different organitation le-els (e.g. tissues)
Di-ersity in number* type and sy,e
/iruses are not properly organisms
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Eukaryotes
1Eu2 good*
13aryo2 nut or )ernel
(resence of nucleous
separated from del cytoplasm
by t'e nucleous en-elope.
D4&% double5stranded* it is
organi,ed in c'romosomes
6'e cell contains ot'er
membrane5bound organelles
7eual reproduction is
common
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Prokaryotes
9ac) a cell nucleous
D4&% circular single
stranded
9ac) ot'er
membrane5bound
organelles.
:it'out seual
reproduction alt'oug'
t'ere are genetic
recombination
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Viruses
Contain nucleic acids and
proteins but no ot'er
c'aracteristics
6'ey use t'e cellular
mac'inery of t'eir 'osts
to replicate
4# can replicate outside
t'e 'ost 4#6 li-ing
beings
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Cellular components to scale
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Content
Cells and organisms
Molecules of life (Biomolecules)
6'e central dogma
Genes and gene epression
@: Most pictures have been freely obyained from:
http://www.accessexcellence.org/
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Biomolecules
Biomolecules
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Key biomolecules
6'e basic components of biological systems are
7ugars (carbo'ydrates)
?ats (lipids)
4ucleic acids
(roteins
7ugars and lipids 'a-e no important role
regarding 1biological information2 4ot discussed
'ere
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Nucleic acids and proteins
Molecules t'at contain and transport
information are
D4& (" different nucleotides)
Contains encoded biological information
@4& (" different nucleotides)
Carries information from D4& to proteins
(roteins (2> different amino acids)
?unction and structure of li-ing beings
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Nucleotides
Basic components of nucleic acids
Consisting of
& sugar (@ibose or Deoyribose)
& nitrogen base
& p'osp'ate group
An biological spea)ing Be say CbasesC instead of
nucleotides to describe a string
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DNA nucleotides
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!e pairing bet"een complementary bases
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!e primary structure o# DNA
7eDuence of nuceotides
?orms an unbranc'ed polymer
#rgani,ed in a double5stranded
atgaatcgta ggggtttgaa cgctggcaat
acgatgactt ctcaagcgaa cattgacgac
ggcagctgga aggcggtctc cgagggcgga
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DNA $s %NA
D4& is organi,ed into a complementary double
'eli. @4& does not.
#ne of t'e four bases are different
D4& &* C* G* 6
@4& &* C* G* $
Differ from t'e nucleotide sugar
D4& Deoyribose
&@4 @ibose
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DNA &tructure
'ttp%EEen.Bi)ipedia.orgEBi)iED4&
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DNA strands sense
Eac' D4& strand 'as a polarity%
6'e strand begins Bit' t'e 1st nucleotide 0F5'ydroyl
(or 0F5p'osp'o) group* and
Ends Bit' t'e last nucleotide !F5'ydroyl group
6'e strand goes 0F to !F (CFive prime to three primeC)
6'e tBo D4& strands are antiparallel
#ne goes 0F !F and t'e ot'er goes !F 0F.
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Proteins
'
&mino acid seDuence
'
?orms an unbranc'ed polymer
'
6'ere are 2> different amino acids (&&)
'
6'e )ey function of proteins is in its t'ree
dimensional structure
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Amino acids
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Proteins (#old) into con#ormational structure
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Protein*s structure
(roteins fold into loBest to 'ig'est compleity
le-el%
Primary structure% amino acid seDuence
Secondary structure% regularly repeating local
structures stabili,ed by 'ydrogen bonds.
Tertiary structure% fold into !5dimensional
structures.
Quaternary structure% structure formed by
se-eral protein molecules (protein comple).
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Content
Cells and organisms
Molecules of life (Biomolecules)
Central dogma of molecular biology
Genes and gene epression
@: Most pictures have been freely obyained from:
http://www.accessexcellence.org/
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Central dogma o#
molecular biology
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Central dogma o# molecular biology
Central dogma of molecular biology states t'at
information encoded in D4& is transferred to
proteins t'roug' @4&.
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+rom DNA to proteins
D4& is replicated in a comple process in-ol-ing many
en,ymes% replication replicacin
D4& is copied in a string of complementary messenger
@4& (m@4&)% transcription transcripciGn
An eu)aryotic cells* t'e m@4& is processed procesa
eliminating coding fragments (1splicing2) and migrates
from t'e nucleous to t'e cytoplasm.
6'e m@4& carries coded information to ribosomes
(ribosomal @4&) t'at CreadC and perform protein
synt'esis% translation traslacin
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,- %eplication
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.- ranscription
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/- %NA processing or splicing
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,DNA $s- / %NA0s
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1- Protein synt!esis
6'e m@4& goes to t'e
cytoplasm B'ere it binds
to ribosomes.
Codon% m@4&
information unit.
6'e t@4& brings t'e
complementary && t@4&.
6'e && are bound to t'e
protein to complete t'e
seDuence.
&nimations (1)* (2)
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10 !e genetic code
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Content
Cells and organisms
Molecules of life (Biomolecules)
Central dogma of molecular biology
Genes and gene epression
@: Most pictures have been freely obyained from:
http://www.accessexcellence.org/
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2enes and gene
e3pression
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4!at is a gene5
At is t'e functional and p'ysical unit of
'eredity transmitted from one generation to
t'eir offsprings.
Genes are D4& fragments
Most of t'e genes contain t'e necessary
information for t'e synt'esis of a specific
protein.
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2ene components
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%egulation o# gene e3pression
Genes can be 1turned on2 or 1off2.
Eac' cell epresses (or acti-e or ConC) only a fraction
of t'eir genes.
@emaining genes are repressed (CoffC).
6'e process consisting in acti-ate genes and
suppress ot'ers is gene regulation.
Gene regulation determines%
6'e appearance and different function of different cells types
6'e ability of some cells to react Duic)ly to en-ironmental
c'anges
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6o" genes are regulated5
Gene regulation can occur at any point in t'e process of
epression but often occurs during transcription.
En-ironmental signs or ot'er cells acti-ate proteins
called transcription factor.
6'ey bind to t'e regulatory regions of genes* increasing
or decreasing t'e le-el of transcription 6'ey control t'e
amount of gene product produced by t'e gene in e-ery
moment.
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E3ample7 2enes acti$ation
:it' no HGC
(glucocorticoid
'ormone) genes are
inacti-e
An presence of HGC
genes are acti-ated
and epressed (in
bloc))
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Mutations
Mutations are genetic c'anges randomly
produced or by t'e action of mutagens
(c'emicals* I rays* $/* etc.)
Most are let'al because t'e original && and
nucleotides seDuence is t'e product of millions
of years of e-olution
(roduct of natural selection (or not...)
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Mutations at t!e molecular le$el
& mutation results in a c'ange in t'e order of
nucleotides in t'e genes
Consider for eample t'e peptide
Nucleotides TAC TTA {C}GA TAA TGC ATT
Codons mRNA- AUG AAU {G}CU AUU ACG UAA
Sequence AA- met asn ala ile thr stop
:e can c'ange a nucleotide (eg. 1C22G2) for
anot'er or delete it.
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Point mutations
(oint mutation
7ubstitution of one nucleotide for anot'er
At can be let'al or 'armless (due to t'e degeneracy of
t'e code)
Nucleotides TAC TTA {C}GA TAA TGC ATT
Substitution CG TAC TTA {G}GA TAA TGC ATT
Codons mRNA- AUG AAU {C}CU AUU ACG UAA
New seq. met asn pro ile thr stop
ri!inal seq. met asn ala ile thr stop
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(+rames!i#t) mutation
C'ange t'e reading frame
Deleting a nucleotide c'ange in t'e grouping of
codons
Nucleotides TAC TTA {C}GA TAA TGC ATT
C supression TAC TTA GA"T# AAT GCA TT$
Codons mRNA- AUG AAU CU"A# UUA CGU UA$
New seq. met asn leu arg lys $$$
ri!inal seq. met asn ala ile thr stop
