genetica sibiu

8/12/2019 Genetica Sibiu

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Genetica

Curs introductiv

Maria-Mihaela ANTOFIE


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Genetica

Stiinta ereditatii vietuitoarelor.ereditatea este reprezentata de

procesul transmiterii caracterelorereditare de la parinti la copii.

gennao gr. hereditas lat.

Stiinta de tip meditativ cupreponderenta pana in sec. XIXStiinta de tip experimental cupreponderenta dupa 1905


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Zorii geneticii ca stiinta experimentala

Gregor Mendel ( 1822-1884)

Parintele geneticiirealizeaza experimente pentru

ameliorarea plantelor in gradinamanastirii augustine din BrnoIn 1865 publica prima lucrare stiintificacu privire la unitatile ereditatii

Experiente asupra hibrizilor la plante.


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Gregor Mendel...

Descoperafactorii ereditari (numiti ulterior gene de

catre WL Johannsen in 1909 )modelele de transmitere a caracterelorereditare modele ale ereditatiifaptul ca genele provin de la ambiiparinti spulberand dogma antica de laAnaxagora conform careia doar parteamasculina aduce factorii ereditariconceptul de gene alele, caracterdominant si caracter recesiv


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Gregor Mendel...

Concluziile Mendeliene

hibrizii din prima generatie dupaincrucisare sunt uniformi

gametii sunt intotdeauna puri

perechile de factori ereditari segregaindependent


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1900

lucrarile lui Mendel suntredescoperite simultan de catre

Hugo de Vries OlandaCarl Correns GermaniaErick von Tschermak Austria

este considerat anul de nastereneoficial al geneticii ca stiinta


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Structura ADNnivele de orgnizarebaze purinice A, G

baze pirimidinice T, C

dezoxiriboza

NucleosidePO4(3-)

Nucleotide

NucleosomSolenoidSuprasolenoid

Cromozom


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Baze azotate

Baze pirimidiniceUracil (Ascoli, 1900 din ARN drojdii)Timina (izolata prima data din timus)Citozina (Kossel, 1894)ac orotic precursor in biosinteza bazelorpirimidinice

Bazele puriniceAdenina (Kossel 1885, din pancreas si apoi dindrojdie)Guanina (Magnus, 1844 din guano si apoi

Kossel, 1883, din acizii nucleici)


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Baze azotate...


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Ce anume ne face unici?

Acidul deoxiribonucleic (ADN)Fiecare din cele 100 trilioane de celule ale

unui corp omenesc (1014

) cu exceptiahematiilor contin intreg genomul uman, ininteriorul fiecarui nucleu reasindu-seinformatia completa construirii individului

Functiile ADNdetine codul genetic pentru intreg organismul.furnizeaza informatia necesara sintezeiproteice.


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Lungimea ADN

E. coli 4.64 megabaze (Mb), 1.5776 mmlungime

Drojdia de bere 15 Mbomul 3000 Mb, 1020 mm, sau 1.02m

Genomul are o lungime uriasa in raport cucelula. Astfel, lungimea genomului E. colieste de 1000 ori mai mare decat lungimeabacteriei insasi.


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Bazele azotate ale ADN

Adenina= ATimina= T

Guanina= GCitozina= CA realizeaza duble legaturi de H cu TC realizeaza triple legaturi de H cu G


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Bazele azotate ale ARN

Adenina= AUracil= U

Guanina= GCitozina= CG always pairs with CT din ADN realizeaza duble legaturide H cu A din ARNA din ADN realizeaza triple legaturide H cu U din ARN


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Modelul ADN


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Modelul ADNl


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Chromosomes

The DNA in every cell is located inrod like segments called

chromosomesChromosomes occurs in pairs inevery cell of our body except in the

sperm and ovum.Chromosomes numbers are thesame for each specie.


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E. Pennisi (Nature 2007)


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Chromosome Numbers

Species Diploid # Haploid #Bovine 60 30

Porcine 38 19Oaie 54 27Cal 64 32

Om 46 23Pui 78 39Capra 60 30Magar 62 31


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Chromosomes

There are 2 sex chromosomesincluded in the diploid number of

the chromosomes.All of the other chromosomes arereferred to as autosomes.

In mammals if the sexchromosomes are alike, XX itresults in a female.If the sex chromosomes aredifferent, XY it results in a male.


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Sex DeterminationFemales contribute an X chromosometowards the sex of their offspring.Males can contribute an X or a Ychromosome toward the sex of theiroffspring.Absence of an Y chromosome results in athe embryo developing into a female.Presence of an Y chromosome results inthe embryo developing into a male.


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Sex DeterminationGametogenesis =Formation ofgametes throughmeiosis.Male = 4 viablespermatids

Female = 1 viableovum, 3 polarbodies.


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Tell me what I am ?????


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Tell me what I am ?????


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Cell Division

MeiosisIs the form of cell division which resultsreducing the chromosome number from the

diploid # to the haploid #.Occurs only in the sex cells, sperm andovum.

Mitosis

Is the form of cell division which results inthe formation of identical daughter cells,keeps the chromosome number constant.Tissue growth and repair.Occurs throughout the body except in thesex cells.


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Genotype or Gamete

Genotype contains two copies ofthe gene.

AaBBGamete (sex cells) contains onlyone copy of the gene.

ABDetermine the possible gametes ofAaBB

AB aB


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Gamete or Genotype

State if its a gamete or genotype.Aa

DDdEeFFggsRtxyqAaBBeeFFadgEFT


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List all the possiblegametes.

From the genotype AaBbAB

AbaBab


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GenesCromozomiii contin unitatileereditatii genele.

adesea exista in pereche si isi auoriginea fiecare de la cate unparinte.unele exprima direct un caracterereditar .altele doar in asociere cu alte geneexprima un caracter.


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Genes

It was presumed that we werecomposed of about 100,000 genes

to construct us.Today, research has proven thatnumber is a lot less than 100,000.

Extra credit for the student that canfind an article about the currentnumber of genes.


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Terms to knowHomozygous- contains 2 identicalgenes for the same trait, AA, BB, ccHeterozygous- contains 2 different

genes for the same trait, Aa, bB, CcPhenotype- Outward appearance of atrait, coat color, polled, horned.Genotype- Genetic classification of agene, AA, Aa, aa.Allele- Location of a gene on thechromosome.F-one = First cross mating.F-two = Second cross matin .


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What are dominant genes?

The gene that express itself, thepowerful and dominant gene.

It has the power to overshadow therecessive gene when there is completedominance.Some examples are:

White faced in cattleDroopy ears in swinePolled in cattle

Black coat color in Angus cattle


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What are RecessiveGenes ?

The gene that is overshadowed bya dominant gene

Recessive genes can only expressthemselves in the absence of thedominant genePolled vs Horned (Pp) (pp)Black wool vs white (Ww) (ww)Dwarfism vs normal size (dd)Albino


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Punnet Square

Angus- Black coat color is dominant.BB = Homozygous Dominant and Black

Bb = Heterozygous and is blackbb = Homozygous recessive and redA heterozygous bull is mated to 50homozygous recessive cows.How many calves are black?How many calves are red?What is the genotypic and phenotypicratios?


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Punnet Square

B b

b

b

Bb bb

Bb bb


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Results2 heterozygous =Bb2 HomozygousRecessive bb25 Black, 25 RedGenotypic ratio =

0:2:2Phenotypic ratio =2 Black: 2 Red


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What are Sex LinkedGenes ?

Some recessive genes are attached tothe X and Y chromosomes

Humans: Colorblindness and Baldnessare on the X chromosomesIn Men, traits expressed anytimepresentIn Women, must have two recessives toshow traitChildren get baldness from mothers


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If Dad is bald, will you bebald?

X Y

X X X X Y

X X X YX

B

B

B

B ld i i d b th


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Baldness is carried by themother

X Y

X X X X Y

X X X YX

BB B


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What if Mom is bald?

X Y

X X X X Y

X X X YX

BB B

B B B

Wh i I l


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What is IncompleteDominance ?

If both genes express themselvesShorthorn Cattle: Red male mated

to a White female = Roan calfRR crossed rr = Rr


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Punnet Square

If a red bull (RR) is mated to a roan(Rr) cow, what color will the calves

be?


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Shorthorn: Red X Roan

R R

R

r

RR RR

Rr Rr


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What if Both Parents areRoan?

R r

R

r

RR Rr

Rr rr


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What is a Mutation ?Dramatically different from what isexpected geneticallyHorned calf from polled parentsLoss of some or extra body partsLethal Mutation : causes death at birthSublethal Mutation : limits animalsability to grow to maturityBeneficial Mutation: loss of tail in lambs


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Mating SystemsUpgrading: mating purebreds with gradeanimalsInbreeding: mating closely relatedanimalsLinebreeding: mating distantly relatedanimalsOutcrossing: mating unrelated animals inthe same breed.Crossbreeding: mating animals of samespecies but different breeds.

h i b d ?


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What is Hybrid Vigor ?Heterosis

Offspring will outperform either ofthe parents

Corn Breed A yields 100 bu/acreCorn Breed B yields 100 bu/acreCrossbreed A & B yields corn thatyields 200 bu/acreVigor only expressed incrossbreeding


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The End

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