Biol 301L
Drosophila melanogaster Population Genetics
A short guide to writing the Population Genetics report
Introduction:
The Introduction should provide the reader with all pertinent background
information that is required to understand your experimental results and conclusions.
Therefore, you MUST focus the background information around the biological
mechanisms that YOU suggest are driving your experimental outcome. Provide
suitable/relevant references that ultimately will justify your a priori prediction for the
outcome of your experiment. The final paragraph of the introduction should explicitly
state your hypothesis and predictions.
Hypothesis/Predictions:
Recall your a priori hypothesis/predictions for this experiment. (see worksheet)
Remember to phrase your hypothesis in terms of the experimental variables
measured.
Procedures:
Two Drosophila phenotypes were used to investigate their relative fitness, and
understand how fitness can influence evolution in populations. Students were
responsible for stocking population cages with known proportions of Wild Type and
Vestigial fruit flies. Samples were taken approximately every two weeks to quantify the
allele frequencies of fruit fly populations over a 12 week period. Care and feeding of the
fly populations was carried out by the students.
Data Analysis/Results:
Bi-weekly phenotype frequencies will be used to calculate the allele frequencies
using the Hardy-Weinberg equation. Allele frequencies will be plotted as a function of
time. Final allele frequencies will be statistically compared to initial frequencies using a
Chi-Square analysis.
Discussion:
The discussion section should provide the reader with a coherent, focused
argument convincing the reader that your interpretation of the results is the best
biological explanation.
Based on the data analyzed by your group, discuss the potential BIOLOGICAL
reasons WHY fruit fly allele frequencies changed over time (or did not change over
time). Compare your results to OTHER RESEARCH and PROVIDE CITATIONS to
justify your claims.
Potential biological mechanisms for allele frequency changes are outlined by the
Hardy-Weinberg equation and its assumptions. Note that some mechanisms are likely to
have a greater influence than others on the outcome of your experiment. Recall that
Hardy-Weinberg provides a null model for evolution (conditions in which evolution
should not occur) (e.g. the assumptions). Significant differences in allele frequencies
(calculated by Chi-Square) indicate a violation of one or more assumptions of HardyWeinberg.