“Evolution Lab 1” Examining the Effects of Genetic Drift and Natural Selection using both Beads and Beans Simulations.

 “Evolution Lab 1”

Examining the Effects Genetic drift and Natural Selection using both Beads and Beans Simulations.

 Bio Battlers: Asmah Tadmori, Rama Tadmori, Lia Andrews, Tianzhi Jiang.

Hypothesis: The frequency of alleles (beads’ colours) will significantly change in a population over the course of ten generations due to the random sampling of beads, thus indicating genetic drift occurred.

Null Hypothesis: No statistical significance will occur in the allele frequencies (bead colors) over the course of ten generations due to random sampling.

Predictions: Some alleles (beads’ colors) will start to appear more frequently while others start to reduce in size in a population from one generation to another as a result of random sampling.

Observed Results

Figure 1: This graph represents the changes in 4 different allele frequencies through 10 generations for population A, with a population size of 50. The 4 different alleles were modelled by 4 different colors of beads (red, clear, navy, and white). As demonstrated by the rising and falling values, some colors of beads disappeared, such as the white beads, while colors such as the red beads increased in frequency.

Figure 2: This graph represents the changes in 4 different allele frequencies through 10 generations for population B, with a population size of 50. The 4 different alleles were represented by 4 different colors of beads (red, clear, navy, and white) in the simulation. As demonstrated by the graph, the 4 different colors decreased and increased without significant change. Nonetheless, we notice that the clear beads decreased more significantly than the other 3 alleles.

Chi-Square Analysis

Table1.Chi Square analysis for population A:

	Expected	Observed	O-E	(O-E)2	(O-E)2/E
Red	13	21	-8	64	4.92
Clear	15	15	0	0	0
Navy	11	14	3	9	0.818
White	11	0	-11	121	11

 Df= 3       chi square value=16.73             chi square critical value=7.82

Table2. Chi Square analysis for population B:

	Expected	Observed	O-E	(O-E)2	(O-E)2/E
Red	12	17	5	25	2.08
Clear	10	5	-5	25	2.5
Navy	14	18	4	16	1.14
White	14	10	-4	16	1.14

Df=3      chi square value=6.86            chi square critical value=7.82

Analysis and Conclusion:

We conclude that genetic drift process occurred in population A due to random sampling. Our results support our hypothesis, which indicates that the frequency of alleles will significantly change from one generation to another due to random sampling. As Figure 1 shows, the red bead alleles increased while the white alleles died off at generation 5.  The colorless and black beads increased and decreased interchangeably due to random selection. After applying the Chi-square calculations to population A, we can reject the Null Hypothesis. The critical value was 7.82 and the degrees of freedom was 3, but population A had a calculation of 16.73 for its chi-square value. Population A demonstrated no significant statistical difference in its allele frequencies by the end of the experiment.

For population B, we cannot reject the null hypothesis. We can see from Figure 2 that the four bead colors (red, clear, black, and white) were also increasing and decreasing due to random selection. However, there are not enough signs that indicate that population B has undergone genetic drift. If we look at chi-square analysis of population B, we can see that our chi-square value of 6.86 is less than our chi-square critical value which of 7.82, which means that there’s no significant difference in our expected and observed values in population B. Thus, we must accept the null hypothesis in population B.