10 POPULATION GENETICS Flashcards
- Members of a species can interbreed & produce fertile offspring
Gene Pool
____ have a shared gene pool
species
- all of the alleles of all individuals in a population
Gene Pool
- Different species ____ exchange genes by interbreeding
do NOT
- Different species that interbreed often produce ____
example?
sterile or less viable offspring
e.g. mule
- A group of the same species living in an area
population
- Formation of new species
- One species may split into 2 or more species
- Requires very long periods of time
speciation
- Combines Darwinian selection and Mendelian inheritance
Modern Synthesis Theory
study of genetic variation within a population
- Population genetics
MST emphasizes on ____
quantitative characters (height, size …)
- 1940s – comprehensive theory of evolution
Modern Synthesis Theory
who introduced MST
Fisher & Wright
- Recognizes that ____ are responsible for the inheritance of characteristics
GENES
- Recognizes that ____, not ____, evolve due to natural selection & genetic drift
POPULATIONS
individuals
- Recognizes that SPECIATION usually is due to the ____ of small genetic changes
gradual accumulation
- The modern synthetic theory of evolution describes the evolution in terms of ____ in a population that leads to the formation of a new species.
genetic variations
- Changes occur in gene pools due to mutation, natural selection, genetic drift, etc.
Microevolution
- Gene pool changes cause more ____ in individuals in the population.
Example?
VARIATION
Bacteria becoming unaffected by antibiotics (resistant)
- the process of heredity in a random mating population does not change either allelic frequencies or genotypic frequencies at a given locus
Hardy-Weinberg Principle
Hardy-Weinberg Principle used to describe a?
non-evolving population
HWP
- Shuffling of alleles by meiosis and random fertilization have ____ on the overall gene pool
no effect
- ____ are NOT expected to actually be in Hardy-Weinberg equilibrium
Natural populations
- Deviation from Hardy-Weinberg equilibrium usually results in ____
evolution
- Understanding a non-evolving population, helps us to understand how evolution occurs
5 Assumptions of the H-W Principle
- large population size
- no migration
- no net mutations
- random mating
- no natural selection
Traits selected for random mating
mimicry
color
The gene pool of a NON-EVOLVING population remains ____ over multiple generations
CONSTANT
The Hardy-Weinberg Equation:
1.0 = p2 + 2pq + q2
p2 = frequency of AA genotype
2pq = frequency of Aa
q2 = frequency of aa genotype
Allele Frequency using Hardy-Weinberg
1.0 = p + q
p = frequency of A allele
q = frequency of a allele
5 Causes of Microevolution
- genetic drift
- natural selection
- gene flow
- mutation
- non-random mating
the change in the gene pool of a small population due to chance
genetic drift
success in reproduction based on heritable traits results in selected alleles being passed to relatively more offspring (Darwinian inheritance)
- Cause ____ of Populations
natural selection
ADAPTATION
is genetic exchange due to the migration of fertile individuals or gametes between populations
gene flow
a change in an organism’s DNA; can be transmitted in gametes to offspring
mutation
Mates are chosen on the basis of the best traits
non-random mating
2 Factors that Cause Genetic Drift
bottleneck effect
founder effect
- a drastic reduction in population (volcanoes, earthquakes, landslides …)
- Reduced genetic variation
bottleneck effect
In bottleneck effect, ____ population may not be able to adapt to new selection pressures
Smaller
- occurs when a new colony is started by a few members of the original population
- Reduced genetic variation
- Founder Effect
May lead to speciation
founder effect
example of
Loss of Genetic Variation
- Cheetahs have little genetic variation in their gene pool
- This can probably be attributed to a population bottleneck they experienced around 10,000 years ago, barely avoiding extinction at the end of the last ice age
3 Modes of Natural Selection
- directional selection
- disruptive selection
- stabilizing selection
- Favors individuals at one end of the phenotypic range
- Directional Selection
- Most common during times of environmental change or when moving to new habitats
- Directional Selection
- Favors extreme over intermediate phenotypes
- Disruptive selection
- Occurs when environmental change favors an extreme phenotype
- Disruptive selection
- Favors intermediate over extreme phenotypes
- Stabilizing Selection
- Reduces variation and maintains the current average
- Stabilizing Selection
human birth weight is an example of what mode of natural selection? and how?
stabilizing selection
if high, obesity
if low, malnourish
5 variations in populations
- geographic variations
- hetezogote advantage
- mutations
- genetic recombination
- co-evolution
- Mutations
-In stable environments, mutations often result in little or no benefit to an organism, or are often harmful
-Mutations are more beneficial (rare) in changing environments
example?
HIV resistance to antiviral drugs
source of most genetic differences between individuals in a population
genetic recombination
Often occurs between parasite & host and flowers & their pollinators
co-evolution
- Favors heterozygotes (Aa)
- Maintains both alleles (A,a) instead of removing less successful alleles from a population
heterozygote advantage
example of heterozytote advantage
- Sickle cell anemia
o Homozygotes exhibit severe anemia, have abnormal blood cell shape, and usually die before reproductive age.
o Heterozygotes are less susceptible to malaria
