Gen(Struktur Dan Fungsi)

7/28/2019 Gen(Struktur Dan Fungsi)

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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

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