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Genetic Genetic

recombinationrecombination

Genetic Genetic

recombinationrecombination

Genetic recombinationGenetic recombinationGenetic recombinationGenetic recombination

Obtaining of new gene combinations by Obtaining of new gene combinations by

rearrangements in genetic materialrearrangements in genetic material::

Between two DNA moleculesBetween two DNA molecules

Between two different chromosomes Between two different chromosomes

Between two sets of chromosomesBetween two sets of chromosomes

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Biological importance of Biological importance of

recombinationrecombination

Biological importance of Biological importance of

recombinationrecombination

Genetic variabilityGenetic variability

Natural selectionNatural selection

Biologic evolutionBiologic evolution

Recombination and phenotype Recombination and phenotype

consequencesconsequences

Recombination and phenotype Recombination and phenotype

consequencesconsequences

Genetic polymorphismGenetic polymorphism

Normal phenotypic polymorphismNormal phenotypic polymorphism

Different reaction to environmentDifferent reaction to environment ((drugsdrugs, ,

foodfood, , toxinstoxins...)...)

Susceptibility to infectionsSusceptibility to infections

Predisposition to diseasesPredisposition to diseases ((cancerscancers, ,

diabetesdiabetes...)...)

Abnormal phenotypic polymorphismAbnormal phenotypic polymorphism

Types of recombinationTypes of recombinationTypes of recombinationTypes of recombination

GenomicGenomic –– betweenbetween andandgenomes genomes 23 c23 chhrsrs + 23 + 23 cchhrsrs = 46= 46

ChromosomalChromosomal

InterchromosomalInterchromosomal –– between nonbetween non--homologous chromosomeshomologous chromosomes;;

IntrachromosomalIntrachromosomal –– between between homologous homologous chromosomeschromosomes

Gene Gene –– between two alleles by between two alleles by gene fusiongene fusion

During

fertilisation

During

meiosis

During

meiosis

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????

What dose fertilization representsWhat dose fertilization represents??

Fusion of two sexual cells of different origin Fusion of two sexual cells of different origin

((haploid gametes; haploid gametes; 23 23 chrschrs) ) formation of formation of

zygotezygote ((diploid cell diploid cell 46 46 chrschrs).).

What does meiosis representsWhat does meiosis represents??

Formation of haploid cells called gametes Formation of haploid cells called gametes ((by by

reductionalreductional division a cell withdivision a cell with 46 46 chrschrs

makes haploid cells with 23 makes haploid cells with 23 chrschrs))

Passing of genetic material from parents to childrenPassing of genetic material from parents to children

Fertilization

Zigot

(2n)

Mitosis,

differentiation,

growing

Mitosis,

differentiation,

growing

Copil

(2n) Adulţi

(2n)

Meiosis

Sperm (n)

Egg (n)

Peculiarities of segregation of chromosomes in meiosis

during ovogenesis and spermatogenesis

OVOGENESISOVOGENESIS

SPERMATOGENESISSPERMATOGENESIS

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Mitosis Mitosis vs. vs. MeiosisMeiosisMitosis Mitosis vs. vs. MeiosisMeiosis

46 SC chrs46 SC chrs

46 BC chrs 46 BC chrs

46 SC

chrs

46 SC

chrs

Mitosis

Replication

Meiosis

Replication

23 BC

chrs

23 SC

chrs

23 SC

chrs

23 SC

chrs

23 SC

chrs

23 BC

chrsI

IISomatic cells

Sexual cells = gametes

MitosisMitosis MeiosisMeiosis

! Bivalents at equator

! BC Chrs to poles

! n=2c

! n=c

2n=4c

2n=2c 2n=2c

2n=2c

! MC Chrs to

poles

MIMI

AIAI

TITI

MIIMII

AIIAII

TIITII

MM

AA

TT

MeiosisMeiosisMeiosisMeiosis

I I division division –– reductionalreductional ((2n2n==4c4cn=n=2c2c)) Prophase Prophase II

Metaphase Metaphase I I

AnaphaseAnaphase II

Telophase Telophase II

II II Division Division –– equationalequational (n=(n=2c2cnn=c)=c) Prophase Prophase IIII

Metaphase Metaphase III I

AnaphaseAnaphase IIII

Telophase Telophase IIII

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Meiosis Meiosis I I –– reductionalreductionalMeiosis Meiosis I I –– reductionalreductional

Prophase Prophase II

Condensation of chromosomesCondensation of chromosomes

Formation of spindleFormation of spindle

!!! !!! Conjugation of homologous Conjugation of homologous chromosomes chromosomes bivalents bivalents

!!! !!! CrossingCrossing--overover intrachromosomalintrachromosomalrecombinationrecombination

There are 5 phasesThere are 5 phases: : L, P, Z, D, L, P, Z, D, DD

Prophase Prophase IIProphase Prophase II

LeptotenLeptoten ZigotenZigoten PahitenPahiten DiplotenDiploten DiachinezăDiachineză

Chromatin

condensation

!!! Conjugation

of homologous

chromosomes

!!! Crossing-

over

Pushing of

chromosomesChiasma

termination

Conjugation of homologous Conjugation of homologous

chromosomeschromosomes

Conjugation of homologous Conjugation of homologous

chromosomeschromosomes

Takes place during prophase ITakes place during prophase I

Synapses of homologous Synapses of homologous

chromosomeschromosomes

Ensured by Ensured by synaptonemalsynaptonemal complexcomplex

Importance Importance –– formation of bivalentsformation of bivalents

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SynaptonemalSynaptonemal complexcomplexSynaptonemalSynaptonemal complexcomplex

ScaffoldRecombination

nodules

Chromatin of

paternal sister

chromatids

Chromatin of

maternal sister

chromatids

CrossingCrossing--overoverCrossingCrossing--overover

Takes place during prophase ITakes place during prophase I

Exchange of fragments between Exchange of fragments between

homologous chromosomes homologous chromosomes

intrachromosomalintrachromosomal recombinationrecombination

Determined by Determined by synaptonemalsynaptonemal complexcomplex

Importance Importance –– genetic variabilitygenetic variability

Crossover

gametes

Non-crossover

gametes

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Molecular mechanism of Molecular mechanism of

crossingcrossing--overover

Molecular mechanism of Molecular mechanism of

crossingcrossing--overover

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Metaphase Metaphase IIMetaphase Metaphase II

Bivalents at equatorBivalents at equator

!!! !!! Random orientation of chromosomes to Random orientation of chromosomes to

polespoles

or

Important

Anaphase Anaphase IIAnaphase Anaphase II Disjunction of homologous chromosomesDisjunction of homologous chromosomes

Migration of BC chromosomes to poles Migration of BC chromosomes to poles ((nnchromosomes to each poleschromosomes to each poles))

!!! !!! Independent combination of nonIndependent combination of non--homologous chromosomes homologous chromosomes = = interchromosomalinterchromosomal recombinationrecombination 22nn

combinationcombination

or or or

AbC aBc ABC abc Abc aBC ABc abC

InterchromosomalInterchromosomal recombinationrecombinationInterchromosomalInterchromosomal recombinationrecombination

Takes place during anaphase ITakes place during anaphase I

Between nonBetween non--homologous maternal and homologous maternal and

paternal chromosomespaternal chromosomes

Random separation of nonRandom separation of non--homologous homologous

chromosomeschromosomes

Importance Importance genetic variability of genetic variability of

gametesgametes

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Telophase Telophase IITelophase Telophase II

Reorganization of two nucleiReorganization of two nuclei (n=(n=2c2c))

CitokinesisCitokinesis

Two gametocytes (haploid, Two gametocytes (haploid,

chromosomes BC)chromosomes BC) !!! !!! Reduction of Reduction of

number of chromosomesnumber of chromosomes

2n=4c

n=2c

n=2c

InterkinesisInterkinesisInterkinesisInterkinesis

Preparation to second division Preparation to second division ((meiosismeiosis II)II)

Meiosis Meiosis II II –– equationalequational divisiondivisionMeiosis Meiosis II II –– equationalequational divisiondivision

Prophase Prophase IIII

Formation of spindleFormation of spindle

Maturation of Maturation of kinetocoreskinetocores

andand

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Metaphase Metaphase IIIIMetaphase Metaphase IIII

At equator SC chromosomesAt equator SC chromosomes

andand

AnaphaseAnaphase IIIIAnaphaseAnaphase IIII

Longitudinal cleavage of centromereLongitudinal cleavage of centromere

Disjunction of chromatidsDisjunction of chromatids

Migration of SC chromosomes Migration of SC chromosomes (n=c (n=c cchhrsrs))

andand

TelophaseTelophase IIIITelophaseTelophase IIII

Reorganization of nuclear envelopes and Reorganization of nuclear envelopes and formation of haploid nucleiformation of haploid nuclei ((n=c)n=c)

CytokinesisCytokinesis

4 haploid gametes4 haploid gametes

2n=4c

n=2c

n=2c

n=c

n=c

n=c

n=c

I div

II div

II div

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Biological importance of meiosisBiological importance of meiosisBiological importance of meiosisBiological importance of meiosis

Maturing of gametesMaturing of gametes

Genetic recombinationGenetic recombination

Multiplication of gametesMultiplication of gametes

2n=4c

n=2c

n=2c

n=c

n=c

n=c

n=c

I div

II div

II div

Ovogenesis Spermatogenesis

Ovogonia Spermatogonia

1st ovocyte1st spermatocyte

2nd ovocyte 2nd spermatocytes

Polar body

Polar bodies

Spermatides

Spermatozoons

Spermatozoons

Zygote

Egg

Replication Replication

Meiosis I (reductional) Meiosis I (reductional)

Meiosis II (equational) Meiosis II (equational)

Fecundation)

Formation of

sperms

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Molecular biologyMolecular biologyMolecular biologyMolecular biology

Theoretic support for other subjectsTheoretic support for other subjects

Genetics Genetics

HistologyHistology

BiochemistryBiochemistry

PhysiologyPhysiology

Understanding of molecular and cellular Understanding of molecular and cellular

organization of human organismorganization of human organism

Knowledge of material support of heredity Knowledge of material support of heredity and variabilityand variability

Knowledge of material support of Knowledge of material support of human human pathologypathology

Knowledge of Knowledge of methods of diagnostic at methods of diagnostic at molecular levelmolecular level

Knowledge of Knowledge of bases of modern bases of modern biotechnologiesbiotechnologies

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Quality of DNAQuality of DNAQuality of DNAQuality of DNA

Quality and quantity of Quality and quantity of

cellular and extracellular cellular and extracellular

proteinsproteins

Quality and life lengthQuality and life length

Knowledge Knowledge ------ key of success key of success

for modern medicinefor modern medicine