Evolution Lab 1: Illustration of Genetic Drift through Different Colored Beads

By Team Krusty Krab: David Tang, Jonathan Tang, Shane Hall, and Tommy Taslim

Hypothesis: Genetic Drift will change the allele frequency in a population over time, due to chance. Over generations, allele frequency will keep on changing and create certain patterns. It is predicted that when a certain frequency of allele starts to degrade, some other allele will increase in their frequency.

Figure 1. Allele frequency in Population A demonstrated through 50 beads of varying colors.  The beads were randomly divided and doubled throughout the course of 10 generations to show how the population’s gene distribution changes over time.

 

Figure 2. Allele frequency in Population B shown with different colors of beads.  50 beads were obtained, divided randomly, and doubled over 10 generations to illustrate the population’s gene distribution over time.  

Table 1: The calculation of chi-squared in population A.

Table 2:The calculation of chi-squared in population B.

Null hypothesis: There’ll be no change in allele frequency overtime.

Conclusion: Our results support that genetic drift affects the allele frequency over time. In figure 1, it can be seen that when the allele “clear bead” decreases over time, other alleles start to increase, especially the “white” allele. This pattern can also be seen on generation 8 where the “white” allele decreased while the “red” allele increased, which followed our prediction. Furthermore, overall change is apparent when viewing Figure 1 at generation 1 (expected) and generation 10 (observed). At Generation 1, the allele frequency for all colored beads are close to each other, whereas in the end at generation 10, the allele frequency for each bead changes with clear having experienced the most change in frequency .

Referring to population B in Figure 2, it can be seen that the allele frequencies at generation 10 were different, in that they are not as close as they were in generation 1. It can also be seen on Figure 2 that generation 8 shows the “clear” allele increased drastically, while other alleles seemed to have decreased on that very generation. These 2 figures support both our prediction and our hypothesis that there will be change in allele frequency overtime. To support our hypothesis further, a chi squared test was done to check the validity of our experiment. Our results show that there are statistically significant difference between the observed and expected results for both population A and B. With all the data considered, we rejected the null hypothesis and accepted the alternate hypothesis that genetic drift did alter the allele frequency overtime.