Download genetics regularities of populations

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
2014
GENETICS REGULARITIES OF POPULATIONS
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)
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CAN YOU RECOGNIZE POPULATIONS ?
KINDS OF POPULATIONS
1) autogamic population
individuals reproduce by autogamy (selffertilization)
 each individual produces both male and
female gametes
 the new individual is formed by the fusion
of gametes originating from one individual
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GENETICS REGULARITIES 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
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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
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HARDY-WEINBERG LAW

in virtue of Hardy-Weinberg´s law
can be figured out genotypical
composition of panmictic
population
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
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HARDY-WEINBERG LAW
frequency of dominant allele at a
specific gene in the gene fund of
population
valid for panmictic populations
platí:
p
p+q=1
(100%)
frequency of the recessive allele
q
probability of encountering two
dominant alleles (arising a
dominant homozygot)
p x p = p2
probability of encountering two
recessive alleles
q x q = q2
probability of arising a heterozygot
(p x q)+(q x p) = 2pq
so total genotypic composition of
population stands good
p2 + 2pq + q2 = 1
GENETICS REGULARITIES OF POPULATIONS
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

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 highest
Is in Middle Asia and lowest in northeast Spain. It is still remarkable consequence
Og 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 of
Panmictic 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
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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).
SOURCES

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