Genetic Evolution in Mouse Population: Lab Report

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Abstract

The Mice Population Experiment investigated the dynamics of allele frequency change and evolution in a population of mice. The experiment consisted of eight events, including natural selection, gene flow, and genetic drift, which influenced the population's genetic traits, specifically fur color, fur thickness, and jaw strength. The results revealed significant fluctuations in allele frequencies over time, indicating the occurrence of mutations and evolution within the mouse population. This report provides a comprehensive analysis of the experiment's findings, including tables, calculations, and explanations of the observed genetic changes.

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Introduction

In this experiment, we examined the genetic evolution of a mouse population over eight events. These events included both nonrandom and random factors, such as extreme weather, forest fires, emigration, and mutations, which affected the mice's traits and allele frequencies. The three traits under investigation were fur color (brown and white), fur thickness (thick and normal), and jaw strength (strong and normal). The experiment aimed to assess how these genetic traits evolved in response to various environmental challenges and selective pressures.

Methods

For this experiment, a population of mice with the following traits and allele frequencies was initially established:

Trait	Allele Frequency (p)	Allele Frequency (q)
Fur Color (B/b)	0.50	0.50
Fur Thickness (T/t)	0.50	0.50
Jaw Strength (J/j)	0.50	0.50

Throughout the experiment, allele frequencies for these traits were recorded after each event to track changes in the population's genetic makeup. We used the Hardy-Weinberg equation to calculate allele frequencies, where p represents the dominant allele frequency, and q represents the recessive allele frequency:

p² + 2pq + q² = 1

Results

The results of the experiment showed significant fluctuations in allele frequencies for all three traits.

Table 1 summarizes the initial and final allele frequencies for each trait after the eight events:

Event	Trait	Initial p	Initial q	Final p	Final q
1	Fur Color (B/b)	0.50	0.50	0.57	0.43
	Fur Thickness (T/t)	0.50	0.50	0.73	0.27
	Jaw Strength (J/j)	0.50	0.50	0.02	0.98
	2	Fur Color (B/b)	0.57	0.43	0.60	0.40
		Fur Thickness (T/t)	0.73	0.27	0.40	0.60
		Jaw Strength (J/j)	0.02	0.98	0.90	0.10
		3	Fur Color (B/b)	0.60	0.40	0.65	0.35
			Fur Thickness (T/t)	0.40	0.60	0.50	0.50
Jaw Strength (J/j)			0.90	0.10	0.85	0.15
4			Fur Color (B/b)	0.65	0.35	0.67	0.33
			Fur Thickness (T/t)	0.50	0.50	0.55	0.45
	Jaw Strength (J/j)		0.85	0.15	0.80	0.20
	5		Fur Color (B/b)	0.67	0.33	0.68	0.32
			Fur Thickness (T/t)	0.55	0.45	0.60	0.40
		Jaw Strength (J/j)	0.80	0.20	0.78	0.22
		6	Fur Color (B/b)	0.68	0.32	0.70	0.30
			Fur Thickness (T/t)	0.60	0.40	0.63	0.37
Jaw Strength (J/j)			0.78	0.22	0.75	0.25
7			Fur Color (B/b)	0.70	0.30	0.71	0.29
			Fur Thickness (T/t)	0.63	0.37	0.62	0.38
	Jaw Strength (J/j)		0.75	0.25	0.75	0.25
	8		Fur Color (B/b)	0.71	0.29	0.71	0.29
			Fur Thickness (T/t)	0.62	0.38	0.62	0.38
		Jaw Strength (J/j)	0.75	0.25	0.90	0.10

Discussion

The experiment's results demonstrated that allele frequencies for fur color, fur thickness, and jaw strength underwent significant changes over the eight events. These fluctuations in allele frequencies indicate the occurrence of mutations and evolution within the mouse population.

During the experiment, various factors influenced allele frequencies. Event 1, the Ice Age, favored white mice with thicker coats due to extreme cold, causing an increase in the frequency of the B allele and T allele. Subsequent events, including forest fires (Event 2), emigration (Event 3), and extreme weather (Events 4-6), continued to affect allele frequencies, with white mice remaining favored in the environment.

Event 7 introduced gene flow through immigration, but it did not significantly alter the predation rate, as the brown mice still remained favored over white mice. Finally, Event 8, a mutation affecting jaw strength, resulted in a sharp decrease in the frequency of the J allele.

The observed changes in allele frequencies can be attributed to the principles of evolution, including natural selection, gene flow, and genetic drift. Natural selection played a crucial role in shaping the population's genetic makeup by favoring traits that were advantageous in specific environmental conditions. Gene flow introduced genetic variation through immigration, while genetic drift, exemplified by events like forest fires, influenced allele frequencies through random events.

The experiment's findings align with the hypothesis that evolution occurs in response to environmental pressures. The fluctuation in allele frequencies throughout the experiment confirms that mutations and natural selection played pivotal roles in shaping the population's genetic traits over multiple generations.

Conclusion

The Mice Population Experiment provided valuable insights into the dynamics of allele frequency change and evolution within a mouse population. The results demonstrated that mutations and environmental factors, including natural selection, gene flow, and genetic drift, influenced the population's genetic traits over time.

Understanding the process of evolution in a controlled setting, as demonstrated in this experiment, can help scientists gain insights into how organisms adapt to their environments and develop new species over generations. The study of evolution is essential for advancing our knowledge of how life on Earth has evolved and can provide valuable insights into human evolution and the origins of different species.

This experiment serves as a valuable contribution to the field of evolutionary biology, highlighting the intricate interplay between genetics and environmental factors in shaping the genetic diversity of populations.