Gene Frequency vs. Natural
Selection
Team Married 2 The Game
What is Natural Selection and Gene
Frequency?
Natural Selection
●
●
●
The process theorized by Charles Darwin
wherein organisms adapt to their
environment over time and live to
produce offspring.
Weeds out the unfit individuals
Selective towards traits best suited for
environment
Gene Frequency
●
●
The ratio of a particular allele to the
total of all other alleles of the same gene
in a given population
Also known as allele frequency
Relationship
● Gene frequency gravitate to remain constant from generation to
generation if the requirements for Hardy-Weinberg Equilibrium are met.
● Natural Selection is one of the factors that interferes with the
equilibrium of gene frequency and the gene pool.
● However, Natural Selection enhances individuals that are well adjusted
to the biological and physical conditions of their environment.
● Therefore, organisms with the best adaptations are more likely to
survive, reproduce, and pass their successful alleles onto their offspring.
Relationship cont...
Unfavourable alleles
Decrease
(Green)
Unfavourable alleles
Increase
(tan)
Methods for Natural Selection
●
Natural Selection, a force in nature associated with evolution, was
modeled.
●
The key components for modeling this experiment involved using
different colored dots to represent different specimens within a
population, these different specimens were placed on different
patterned maps to simulate them in different environments, student
predators were introduced with different capabilities.
●
Observed were several rounds of predation effects on several different
specimens within a population in two different environments, while
measuring specimen survival rate and growth rate of offspring to observe
heritable traits for natural selection and natural selection resulting in
adaption.
Natural Selection Results
Light Blue species suffered one of
the highest number of deaths in
environment one.
●
Least adapted for:
o
Environment one (tied for most
deaths, highest % of total deaths in
env. 1: 65/35)
Tiffany Blue suffered the highest
number of deaths in environment
two.
●
Least adapted for:
o
new environment (67% of total env. 2
deaths)
o
natural disasters (highest # of deaths)
Similar colors experienced opposite
results in both environments.
Methods for Gene Frequency
Beads were use to represent species in a population.
Two beads were randomly paired and their genotype is recorded.
Gene frequency change, a mechanism associated with microevolution, was modeled
Scenario 1
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Place 50 Red Beads and 50 White Beads
in a cup.
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Randomly pair to create RR homozygous
dominant, Rw heterozygous, and ww
homozygous recessive.
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33% of ww homozygous recessive are
selected against and place into death
cup per gen in 5 generations
Scenario 2
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100% of ww homozygous recessive is
selected against per each gen in 5
generations
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Scenario 3- Positive Mutation
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Use 40 Red, 40 White, and 20 Green
Beads.
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Randomly sort pairs to create
- RR Homozygous dominant, Rw Heterozygous,
ww homozygous recessive, RB Heterozygous, wB
Heterozygous, and BB homozygous.
- 100% of ww is selected against, a positive
mutation for 150% of RB Heterozygous, and 200%
of BB. (Per each gen in five generations)
Forecast data was calculated using slope equations from logarithmic trend lines
for individual populations in each scenario. (see figures 6,7,8,9 in lab report)
Scenario 4- Negative Mutation
●
Using 40 Red, 40 Green, and 20
Yellow Beads, randomly sort pairs to
create
-RR Homozygous dominant, Rw
Heterozygous, ww homozygous recessive, RB
Heterozygous, wB Heterozygous, and BB
homozygous.
- 100% of ww Homozygous recessive is
selected against, 50% of RB Heterozygous is
selected against, and 100% of BB homozygous
is selected against. (Per each gen in five
generations.
Gene Frequency Results
Negative Pressures:
0 % ww | GG
50% RG
Neutral:
RR | Rw | wG
Heterozygous = Rw | wG
Homozygous = RR | GG | ww
Co-Dominant = RG
When a Green allele is inherited with a
Dominant allele it results in lower
survivability.
Allele
Frequency at Gen 1
(Percent of total
allele count)
Frequency at
Generation 6
(Percent of total
allele count)
Forecasted Freq.
at Generation 12
(Percent of total
allele count)
Red
42%
78%
87%
White
39%
19%
13%
Green
19%
3%
0%
Comparison of GF to NS
Organisms with negative pressures
for green mutation that did not
acquire any genetic variations to
help adapt to their environment
quickly perished.
Organisms containing the green
mutation allele became extinct by
generation 10.
In scenario 4, the green mutation is a
perfect example of natural selection
weeding out the unfit individuals and
eliminating the non adapted
population for better suited
organisms in that environment.
Comparison of GF to NS
In Scenario 3, organisms which inherited allele
frequencies of parent organisms due to positive selective
pressures for the green mutation gene have a higher
survival and reproductive rate that is best suited for their
environment.
Organisms adapted to their environment due to heritable
biological traits survived and reproduced with inherited
traits on the differential reproductive success of
organisms interacting with their environment.
Conclusion
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Natural Selection is a gradual process by which organisms with favorable traits tend to have a
higher reproduction rate.
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Gene Frequency is conducive to remaining constant from generation to generation.
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Natural selection is easily reproducible in a laboratory setting; On the other hand, Hardy
Weinberg is not easily reproduced in a lab setting due to restrictions on the population size.
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First Hypothesis: Disproved due to low population size and only six generations.
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Second Hypothesis: Since the co-dominant genotype went extinct (which is a form of natural
selection), we disproved our second hypothesis.
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Third Hypothesis: This hypothesis was supported due to the small population size and survival
rates (which inhibited Hardy Weinberg Equilibrium).
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Our data confirms that there is significant evidence in support of natural selection - however
it is theoretically difficult to recreate an environment where the criteria for hardy-weinberg
equilibria is attainable.
References
● Reece, J., Wasserman, S., Urry, L., Minorsky, P., Cain,
M., & Jackson, R. (2014). The Evolutionary History of
Biological Diversity. In Campbell Biology (10th ed., pp.
467-478). Boston: Pearson.
● Huiming et al. (2014). Allele frequency changes due to
hitchhiking in genomic selection programs. Genetics
Selection Evolution, 46(1): 8. doi: 10.1186/1279-968646-8.