Lecture 2: HWE and Agents of Evolution Flashcards
What is a modern evidence supporting Darwinian evolution?
1)Artificial selection
*proves that selection is an effective evolutionary process
2)Fossils
*sequence they appear = sequence they expected to evolve
3)Anatomy
*confirm that evolution is a remodelling process
Explain what is microevolution?
-evolutionary change in a population
-smallest scale of evolution
-Change in allele frequencies in a population over generations
-Natural selection can lead to changes in allele frequencies
What is the base principle of genetic variation?
differences among individuals in the composition of their genes or other DNA segments
What is the discrete vs quantitative in gene variability?
discrete: phenotypic difference in a SINGLE gene
quantitative: phenotypic differences in two or more genes
What is the definition of a gene pool?
sum of all different alleles in a population
What is a fixed allele?
when only ONE allele exists for a particular gene in the population
What is the principle of allele frequency?
when each allele has a frequency (proportion) in the population
How do you calculate the total number of allele at a locus for a diploid organism?
total number of individuals X2
What is incomplete dominance?
when getting a third genotype
what is the formula to calculate allele frequency?
p + q = 1
What is the principle of Hardy Weinberg equilibrium?
-original frequencies of the genotypes and alleles remains CONSTANT from generation to generation
What are the five things that CAN’T happed to have a HWE?
-No mutation
-No gene flow
-Random mating
-No selection
-population size very large
What is the formula to calculate the genotypic frequency?
p^2 + 2pq + q^2 = 1
What are the five agents of evolutionary change?
1)Mutation
2)Gene Flow
3)Non-random mating
4)Genetic drift
5)Natural selection
What is the principle of mutation
*changes in the nucleotide sequence of DNA
-Introduce new alleles in a population
What is the principle of gene flow?
*movement of alleles from one population to another
How do the alleles transfer in gene flow?
through the movement of fertile individuals (Mate)
Gene flow can increase or decrease fitness in a population?
decrease
What is the principle of non-random mating?
*Individuals with a certain genotype mate with more commonly than would be expected
What is the result of dissortive mating?
increase heterozygosity
What is the result of assortive mating?
increase homozygotes
What is the principle of genetic drift?
*describe how allele frequencies fluate unpredictably form one generation to another
What is the founder effect?
few individuals become isolated from a larger population
What is the bottleneck effect?
a sudden reduction in a population size due to change in environment – gene pool may no longer be reflective
What is the principle of natural selection?
-new genetic variations arise by chance
-beneficial alleles are “sorted”
What are processes that decrease genetic variation of alleles frequencies?
-gene flow
-genetic drift
-stabilizing selection
What process increase genetic variation?
Natural selection
What is the principle of adaptive evolution?
change acting on an organism’s phenotype
What is reproductive fitness?
comparative ability of an organism to survive to reproductive age in a particular environment – produce variable offsprings
What is one rule for a relative fitness problem?
most fit phenotype is assigned a fitness value of 1.0
What shows the selection coefficient?
reduction in fitness compared to the most fit phenotype
What are two process for balancing selection?
-Heterozygote advantage
-Frequency-dependant selection
What is the aim of balancing selection?
-favoring the persistent of multiple alleles at a particular gene locus
What can be prevent by balancing selection?
any single allele from becoming fixed
What is the principle of Heterozygote advantage?
when heterozygote have a higher fitness than do both homozygous – maintaining more alleles at that locus
Explain the example of sickle-cell anaemia in the context of the effect of a point mutation
-causes mutation is hemoglobin – confers malaria resistance
*Region where malaria parasite is common = heterozygote for the sickle-cell allele is favoured
What is the principle of frequency-dependant selection?
*fitness of genotype depends on its frequency
rare traits – provides advantage
What are three type of selection that are traits that are affected by multiple genes?
-directional selection
-disruptive selection
-Stabilizing selection
What is the principle of directional selection?
*favours one end of the phenotypic range
(when members of a population migrate to a new habitat)
What is the principle of disruptive selection?
*favours BOTH extremes of the phenotypic range
What is the principle of stabilizing selection?
favours intermediate variants and act against extreme phenotypes
What is the Hardy Weinberg Principle?
frequency of alleles and genotypes in a population will stay the same from one generation to another
Dominant allele CANT replace respective allele
