2014

GENETICS OF POPULATIONS

Výukový materiál GE 02 - 54

Tvůrce: Mgr. Šárka Vopěnková

Tvůrce anglické verze: ThMgr. Ing. Jiří Foller

Projekt: S anglickým jazykem do dalších předmětů

Registrační číslo: CZ.1.07/1.1.36/03.0005

Tento projekt je spolufinancován ESF a SR ČR

population: a group of individuals of the same species,

living on a specific area individuals can loosely crossbreed among

each other and they arise out of the same ancestor

they have got common gene fund (complex of alleles, which are kept genetically)

GENETICS REGULARITIES OF POPULATIONS

CAN YOU RECOGNIZE POPULATIONS ?

1) autogamic population individuals reproduce by autogamy (self-

fertilization) each individual produces both male and

female gametes the new individual is formed by the fusion

of gametes originating from one individual

KINDS OF POPULATIONS

homozygotic individual (homozygotic dominant homozygotic recessive) can produce only homozygotic descendants

in autogamic population appear permanent decrease of heterozygotes

increasing share of homozygotes

GENETICS REGULARITIES OF POPULATIONS

2) alogamic population the individual arises by the fusion of 2

gametes coming from different individuals a special case is - panmictic population large population which has a non-limited

possibility of reciprocal crossbreed

GENETICS REGULARITIES OF POPULATIONS

panmixia = by no means limited possibility of reciprocal crossbreed of any individual with any other member of the population

every male gamete has identical probability to meet any female gamete

GENETICS REGULARITIES OF POPULATIONS

in virtue of Hardy-Weinberg´s law can be figured out genotypical composition of panmictic population

HARDY-WEINBERG LAW

the law is in force by these conditions (assumptions):

no mutations occur (at least not at the observed gene)

no selection occurs no migration occurs population must be panmictic and very

numerous

valid for panmictic populationsvalid for panmictic populationsfrequency of dominant allele at a frequency of dominant allele at a specific gene in the gene fund of specific gene in the gene fund of populationpopulation

frequency of the recessive allelefrequency of the recessive allele

platí:platí:

p + q = 1 p + q = 1 ((100%)100%)

probability of encountering two probability of encountering two dominant alleles (arising a dominant alleles (arising a dominant homozygot)dominant homozygot)

probability of encountering two probability of encountering two recessiverecessive allelesalleles

probability of arising a heterozygotprobability of arising a heterozygot

so total genotypic composition of so total genotypic composition of population stands goodpopulation stands good

p x p = pp x p = p22

q x q = qq x q = q22

(p x q)+(q x p) = 2pq(p x q)+(q x p) = 2pq

pp22 + 2pq + q + 2pq + q22 = 1 = 1

pp

qq

HARDY-WEINBERG LAW

autogametic and panmictic population: completely different way of reproduction different population– genetic relations in the nature those extreme types rare 100 % self-pollinating plant species does

not exist

GENETICS REGULARITIES OF POPULATIONS

ABO SYSTEM

Frequency of allele IB for basic blood group B (in %) in European populations. Its frequency makes a gradient decreasing from the east to the west. The highestIs in Middle Asia and lowest in northeast Spain. It is still remarkable consequenceOg migration waves – historical invasions of Mongolian Tartars in Europe after the breakdown of Roman. Invaders left there the allele IB in their descendants.

GENETICS REGULARITIES OF POPULATIONS

Decrease of laetal recessive allele frequency during the rotation ofPanmictic population which is nowadays formed only by heterozygots. Even if Arising recessive homozygots cannot survive, the allele will never disappear because it is still kept in heterozygots (selection pressure does not counteract)

GENETICS REGULARITIES OF POPULATIONS

Hardy - Weinberg balance for 2 alleles

Task 1: In the population (9800 individuals total) there

occurs a hypothetical genetically determined feature.

The dominant form of this feature is conditioned by the dominant allele A, the recessive form of the feature is conditioned by a recessive allele.

Dominant phenotype occurred by 4998 individuals.

Determine the gene frequency of dominant and recessive alleles (the population is in HW balance).

CHALUPOVÁ-KARLOVSKÁ, Vlastimila. Obecná biologie: středoškolská učebnice : evoluce, biologie buňky, genetika : s 558 řešenými testovými otázkami. 2., opr. vyd. Olomouc: Nakladatelství Olomouc, 2010, 206 s. ISBN 978-80-7182-282-0

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