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Influencing Factors on Gene Diversity in Populations

Learn about mutations, selection, migration, genetic drift and their impact on gene frequencies in populations. Explore examples to understand how alleles change over generations.

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Influencing Factors on Gene Diversity in Populations

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  1. 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

  2. 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

  3. 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

  4. 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 FACTORS INFLUENCING GENE FUND OF POPULATION

  5. 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 FACTORS INFLUENCING GENE FUND OF POPULATION

  6. 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 FACTORS INFLUENCING GENE FUND OF POPULATION

  7. genetic shift (drift): • coincidental shift of genetic balance • itis 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 FACTORS INFLUENCING GENE FUND OF POPULATION

  8. 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 FACTORS INFLUENCING GENE FUND OF POPULATION

  9. loss of alleles causes an increased number of homozygots • => it leads to increasing of probability of relational crossbreed - inbreeding FACTORS INFLUENCING GENE FUND OF POPULATION

  10. 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? • Frequency of heterozygotes ? WORKSHEET

  11. 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? WORKSHEET

  12. 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 SOURCES

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