Josh Giersch Biology 2/6/12
Allele shuffling of single gene traits in Drosophila
Purpose: The purpose of the Drosophila experiment is to use fruit flies for genetic crosses to determine the organism’s sex while being able to recognize contrasting phenotypes.
Introduction/Background information: The fruit fly (Drosophila melanogaster) is the organism used in the Drosophila experiment. An average fruit flies life span is approximately two weeks long and that time fruit flies produce a large offspring. The four chromosomes fruit flies have can be found in the cells of the salivary glands. One pair of chromosomes is not homologous making these x and y designated. The female fruit fly has two X chromosomes for sex chromosomes and the male has an X and a Y chromosome. The fruit flies have three other pairs of Chromosomes which are autosomes.
Hypothesis: If the p-value is greater than 5%, then allele shuffling can be said to be random.
Materials: Sorting brushes, sorting cards, fly morgue, stereomicroscope, petri dish of wild-type flies, petri dish of mutant flies, petri dish of F1 flies, culture vial with medium, foam plug, cross vial, fly nap.
Methods: Step 1: Observe all wild type flies under a stereomicroscope.
Step2: Observe mutant types than comparing the mutants to wild type flies finding each mutants phenotype and contrasting the wild type phenotype.
Step 3: Observe F1 flies in a petri dish to record the flies sex and phenotype.
Step 4: In a cup put in instant Drosophila Medium and another cup of water where the liquids solidify so 4-7 grains of yeast may be put on the top.
Step 5: Place six female and male flies in the new vial after the flies are anesthetized.
Step 6: Score all F1 flies and record all data and finish by setting up the F1 cross.
Step 7: Construct two punnett squares to show results of the parent and F1 crosses.
Step 8: Use Fly Nap anesthetic and quickly place all flies in the morgue.
Step 9: Every other day, anesthetize all flies and use a petri dish to find the flies sex and presence of phenotypes.
| Ss X Ss Sepia & Wild eyed | |||||
| Phenotype | Observed | Expected | Chi Square Value | p-Value | Significant(Y/N) |
| Red Eyed | 871 | 897.75 | 0.797 | 5% | No |
| Sepia Eyed | 325 | 299.25 | 2.391 | 5% | No |
| total | 1197 | 3.1 | 5% | No | |
| VvSs X VvSs Vestigial & Wild | |||||
| Phenotype | observed | Expected | Chi Square Value | p-value | Significant (y/n) |
| Vestigial Red | 197 | 15.8 | 22.9 | 5% | yes |
| Vestigial Sepia | 231 | 266.6 | -0.26 | 5% | yes |
| Wild Red | 708 | 5 | 281.2 | 5% | no |
| Wild Sepia | 240 | 1.75 | 272.2 | 5% | no |
| total | 1376 | 289.3 | 5% | yes | |
| Ww & Ww White eyed & Wild | |||||
| phenotype | observed | Expected | Chi Square Valuep-value | Significant (y/n) | |
| white eye male | 228 | 216.6 | 0.6 | 5% | No |
| white eye female | 184 | 216.6 | 4.9 | 5% | No |
| wild male | 240 | 216.6 | 2.5 | 5% | No |
| wild female | 214 | 216.6 | 0.03 | 5% | No |
| total | 866 | 8.06 | yes | ||
Conclusion: The purpose of the Allele shuffling of gene traits project was to use genetic crosses to determine the organism’s sex while being able to recognize different phenotypes. The hypothesis for this project is if the results of the p-value are over 5%, than the shuffling can be random. The data found for the three crosses were the same results p-value wise which means the hypothesis was correct meaning the allele shuffling is random. Based on the data, with the chi square values, all data below 1% was not significant. In the third cross, all of the data for the expected category resulted in the same numbers while the other two crosses data varied. The first cross was rejected while the other two crosses were accepted. One reason the results may have changed may have been due to human error for example flies not sexed properly, flies flying away or the number of flies may have even been miscounted.
