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Structure and FunctionStructure and Function
of Geneof Gene(part I)(part I)
ByByDr.Dr. EstriEstri LarasLaras ArumingtyasArumingtyas
FatchiyahFatchiyah, PhD, PhD
IrfanIrfan Mustafa,SSi.MSiMustafa,SSi.MSi
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Gregor MendelGregor Mendel
One of the pioneers in geneticsOne of the pioneers in genetics
Used scientific approach to understandUsed scientific approach to understand
genetic features:genetic features:
Character: is a heritable feature likeCharacter: is a heritable feature like
flower colorflower color Trait: Each variant for a characterTrait: Each variant for a character
Gregor Mendel in 1857Gregor Mendel in 1857
started tostarted to
experiment with:experiment with:
Pea PlantsPea Plants
Traits:
Character:
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Character Dominant traits Recessive traits
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1857 Experiment
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MendelMendels principle of Segregations principle of Segregation
Pairs of alleles segregate (separate)Pairs of alleles segregate (separate)during gamete formation; the fusionduring gamete formation; the fusion
of gametes at fertilization createsof gametes at fertilization creates
allele pairs againallele pairs again
Ex:Ex: TtTt organismorganism
Each gamete gets either TEach gamete gets either T oror t, but not botht, but not both
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Mendel did not stop hereMendel did not stop here
He went on to cross pea varieties thatHe went on to cross pea varieties that
differed indiffered in six other qualitative traitssix other qualitative traits. In. Inevery case, the results supported hisevery case, the results supported his
hypothesis.hypothesis.
He crossed peas that differed inHe crossed peas that differed in twotwotraitstraits. He found that. He found that the inheritance ofthe inheritance of
one trait was independent of that of theone trait was independent of that of the
otherother and so framed his second rule: theand so framed his second rule: therule of independent assortmentrule of independent assortment..
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MendelMendels principle ofs principle of
Independent AssortmentIndependent Assortment By then doing an F1 cross (By then doing an F1 cross (RrYyRrYy xx
RrYyRrYy) Mendel showed that the allele) Mendel showed that the allelefor yellow (Y) didnfor yellow (Y) didnt always end up int always end up in
the same gamete with the allele forthe same gamete with the allele for
round (R)round (R)
Genes for different traits canGenes for different traits can
segregate independently during thesegregate independently during theformation of gametesformation of gametes
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Animal InheritanceAnimal Inheritance
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Human InheritanceHuman Inheritance
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MendelMendels Models Model Alternative versions ofAlternative versions of
genes account for variationgenes account for variationin inherited charactersin inherited characters
Alleles are alternativeAlleles are alternativeversionsversions
ChromosomeChromosome GeneGene LocusLocus
For each character, anFor each character, anindividual inherits 2 allelesindividual inherits 2 alleles(P1 and P2):(P1 and P2):
Two alleles being differentTwo alleles being differenthave dominant or recessivehave dominant or recessiveallelesalleles
Dominant allele isDominant allele is
expressedexpressed
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Structure and FunctionStructure and Function
of Geneof Gene(part II)(part II)
ByBy
EstriEstri LarasLaras ArumingtyasArumingtyas
FatchiyahFatchiyah
Irfan MustafaIrfan Mustafa
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What is Inheritance?What is Inheritance?
Passing on genetic information fromPassing on genetic information from
parents to offspringparents to offspring Humans have 23 pairs ofHumans have 23 pairs of
chromosomes (46 total)chromosomes (46 total) 1 of each pair is from one parent and1 of each pair is from one parent and
the other is from the other parentthe other is from the other parent
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ChromosomesChromosomes
Chromosomes, threadlike structures,Chromosomes, threadlike structures,
first observed byfirst observed by NageliNageli in 1842.in 1842.
Long strands of DNA that carry theLong strands of DNA that carry thegenetic information on building andgenetic information on building andsustaining a living human being.sustaining a living human being.
Each chromosome contains manyEach chromosome contains manygenesgenes
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What is a Gene?What is a Gene?
A segment of a chromosome thatA segment of a chromosome that
containing the code for a singlecontaining the code for a singleprotein (enzyme)protein (enzyme)
-- The enzyme causes a chemical reactionThe enzyme causes a chemical reaction
that allows a trait to be expressed.that allows a trait to be expressed.ieie. Production of a pigment. Production of a pigment
Something that stated by Mendel asSomething that stated by Mendel asfactorfactor
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RoundRound vsvs WrinkledWrinkled
Dominant allele round codes forDominant allele round codes for enzymeenzymethat converts sugarthat converts sugar starchstarch
Recessive allele have defective enzymeRecessive allele have defective enzyme Sugar accumulatesSugar accumulates
Water diffuses in the seedWater diffuses in the seed Seeds swellSeeds swell
Mature seed when dried becomes wrinkledMature seed when dried becomes wrinkled
One dominant allele produces enoughOne dominant allele produces enoughenzymeenzyme
Both homozygous dominants andBoth homozygous dominants andheterozygotes produce enough enzymeheterozygotes produce enough enzyme
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AllelesAlleles Alleles are alternate forms of aAlleles are alternate forms of a
genegene HomozygousHomozygous individuals have twoindividuals have two
identical alleles for a traitidentical alleles for a trait
ex.: AA or aa organism
HeterozygousHeterozygous individuals have twoindividuals have two
different alleles for a traitdifferent alleles for a traitex.:ex.: AaAa organismorganism
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Chromosomes arethreadlike structures
composed of DNAmolecules
Nucleus (center of cell)containschromosomes andgenes
A gene, asegment of DNA(spiraled double
chain) containingthe hereditary
code
The bodycontains trillions
of cells
Cell, chromosome and gene (DNA)
chromatin
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The Structure of ChromosomeThe Structure of Chromosome
NucleotidesNucleotides ----> DNA> DNA ----> Gene> Gene ---->>ChromosomeChromosome
Human DNA is ~ 2 meters long. TheHuman DNA is ~ 2 meters long. Thenucleus of DNA is about 6nucleus of DNA is about 6 M in diameter.M in diameter.
So, how the very long DNA isSo, how the very long DNA is
packed into a very smallpacked into a very smallnucleus?nucleus?
Ch St tCh St t
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fatchiyahfatchiyah, JB UB, JB UB
Chromosome StructureChromosome Structure
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Type of chromosome structureType of chromosome structure
MetacentricChrom. 1
AcrocentricChrom. 14
SubmetacentricChrom. 9
1.The short arm isdesignated as p andthe long arm as q.
2.The centromere isthe location ofspindle attachment
and is an integralpart of thechromosome.
3.It is essential forthe normalmovement and
segregation ofchromosomesduring cell division.
The ideogram is basically a "chromosomemap" showing the relationship betweenthe short and long arms, centromere(cen). The specific banding patterns are
also illustrated. Each band is numberedto aid in describing rearrangements.
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What molecule transmittingWhat molecule transmitting
genetic inheritance fromgenetic inheritance fromparents to offspring ?parents to offspring ?
DNADNA
((DeoxyriboseDeoxyribose Nucleic Acid)Nucleic Acid)
THE STRUCTURE OF DNA
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THE STRUCTURE OF DNA
DNA: terminology
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nucleoside
base
sugar
DNA: terminology
nucleotides (nucleoside mono-, di-, and triphosphates)
sugarphosphate(s)
base
sugar
DNA: structure
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1. DNA is double stranded2. DNA strands are antiparallel
3. G-C pairs have 3 hydrogen bonds
4. A-T pairs have 2 hydrogen bonds
5. One strand is the complement of the other
6. Major and minor grooves present differentsurfaces
7. Almost all cellular DNA is B-DNA
8. B-DNA has ~10.5 bp/turn of the helix
DNA: structure
Gene expression in eucaryotes and procaryotes
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Gene expression in eucaryotes and procaryotes
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Molecular Definition of GeneMolecular Definition of Gene The entire nucleic acid sequence thatThe entire nucleic acid sequence that
is necessary for the synthesis of ais necessary for the synthesis of afunctional protein and RNAfunctional protein and RNA
Coding region (Coding region (
exonexon
andand
intronintron
) +) +
Regulatory sequences (e.g.Regulatory sequences (e.g.
promoter=promoter=the site where RNA polymerase binds priorthe site where RNA polymerase binds prior
to the initiation of transcriptionto the initiation of transcription))
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Basic Gene StructuresBasic Gene Structures
Eukaryotic genesEukaryotic genes
Exons,intronsExons,introns,,
translation starts and stops, splice (donor/acceptor)translation starts and stops, splice (donor/acceptor)junctionsjunctions
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Basic Gene StructureBasic Gene Structure
Prokaryotic genesProkaryotic genes
coding regions, noncoding regions, non--coding regionscoding regions
translation starts and stopstranslation starts and stops
gene genegenepromoter
start stop
Prokaryotic genes are easier to identify than eukaryotic
genes because of the simplicity of their gene structureand the density of genes in the genome