Transcript factors influencing gene fund of population

FACTORS INFLUENCING
GENE FUND OF POPULATION
Výukový materiál GE 02 - 55
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
FACTORS INFLUENCING GENE FUND OF POPULATION
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mutation:
standing change of gene fund
formation of new alleles
change of a dominant allele on recessive
or on the contrary
frequency very low
important by evolution
standing source of hereditary variability
it enables implementation of selection in
the population
FACTORS INFLUENCING GENE FUND OF POPULATION
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selection - natural:
some phenotypes of features are for their bearer
from the point of view of reproduction
advantageous => individuals have more
descendants
disadvantageous
negative selection – eliminates individuals with
disadvantageous mutant alleles
positive selection – it prefers individuals with better
adaptable genotype
FACTORS INFLUENCING GENE FUND OF POPULATION
consequence of selection:
 is a change of alleles in population
 however, frequency rises with an
advantageous feature
 frequency of alleles decreases with an
disadvantageous feature
 it depends on:
 selection intensity
 type of alleles
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FACTORS INFLUENCING GENE FUND OF POPULATION
if the selection is aimed against
disadvantageous dominant allele =>
allele can disappear
 if the selection is aimed against
disadvantageous recessive allele => the
frequency of the allele decreases in the
population slowly, it never disappears
 selection influences only against
recessive homozygots
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FACTORS INFLUENCING GENE FUND OF POPULATION
migration:
 similar effect like mutation
 enrichment of gene fund by new
alleles or on the contrary also its
impoverishment
 immigration of individuals from
original population
 emigration of individuals from
original population
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FACTORS INFLUENCING GENE FUND OF POPULATION
genetic shift (drift):
 coincidental shift of genetic balance
 it is used in small alogamic populations
 HW law not in force
 some alleles can be eliminated from gene
fund quite randomly only as a result of
insufficient amount of descendants
 the choice of alleles is very small, not
representative
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FACTORS INFLUENCING GENE FUND OF POPULATION
random irregularities appear
 they have a considerable importance in a
small population
 allele frequency still changes between
generations
 changes cannot be predicted
 some alleles are not handed over to the
next generation and disappear, the others
predominate
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FACTORS INFLUENCING GENE FUND OF POPULATION
loss of alleles causes an increased
number of homozygots
 => it leads to increasing of probability
of relational crossbreed - inbreeding
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WORKSHEET
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Example 1:
In a large panmictic population there were
detected 16% of individuals with recessive
form of a qualitative feature (it is a complete
recessivity). What is in this population:
The frequency of both alleles of the gene?
Frequency of dominant homozygotes?
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Frequency of heterozygotes ?
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WORKSHEET
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Example 2.
Blood cells about 84% of the population of our
country have character (agglutinogen) Rh. Blood
group of these people is symbolized Rh +.
Remaining 16% of our population do not have this
character, so they have character Rh-. By the
assumption that the Rh factor is a monogenic
autosomal, dominantly hereditable, Rh + people
are therefore either dominant homozygotes or
heterozygotes.
What is the frequency of Rh allele and particular
genotypes of Rh group in our population?
SOURCES
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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