Fruit Fly -- A project on Drosophila melanogaster
Image Source: http://www.latin.pvt.k12.il.us/DepartmentPages/Science/fruitfly/home.page.html
Sign My Guestbook
View My Guestbook
This is my biology project on Drosophila melanogaster, from the project plan to the final results. As well, I have included an introduction to Drosophila melanogaster from http://www-leland.stanford.edu/~ger/intro.html. There are a couple of links to really good Drosophila web sites. If you have any comments, questions, or ideas, please email me at jennifer.tsai@utoronto.ca.
Drosophila melanogaster is a type of fruit fly. It is commonly used in scientific experiments, chiefly because they have a small number of chromosomes. As well, they have very large chromosomes in their cheeks. This makes the chromosomes very easy to see. They have only 4 pairs of chromosomes (a pair of sex chromosomes and three pairs of autosomes) as compared to the 23 pairs in a human being. This project will be studying the heredity traits of fruit flies' eyes. The colours being studied are red (wild type), brown, purple (black-purple-curved), sepia, and white.
Source: http://www.exploratorium.edu/exhibits/mutant_flies/mutant_flies.html
The drosophila egg is about half a millimeter long. It takes about one day after fertilization for the embryo to develop and hatch into a worm-like larva. The larva eats and grows continuously, moulting one day, two days, and four days after hatching (first, second, and third instars). After two days as a third instar larva, it moults one more time to form an immobile pupa. Over the next four days, the body is completely remodelled to give the adult winged form, which then hatches from the pupal case and is fertile after another day. (timing is for 25ºC; at 18ºC, development takes twice as long.)
Source: http://www-leland.stanford.edu/~ger/intro.html
Problem:
What traits result when fruit flies with different eye colour are crossed?
Hypothesis:
Sepia eye colour would be dominant over all other eye colours, with the darker eye colours always being dominant over the lighter eye colours.
Background Content:
There are only 4 pairs of chromosomes in the fruit fly Drosophila melanogaster as opposed to the 23 pairs in a human being. The fact that these insects have such a small number of chromosomes is the reason why scientists work with them. This study reveals the genetic makeup and heredity traits of fruit flies.
Materials:
Image Source: http://vcourseware2.calstatela.edu/VirtualFlyLab/Images/eyecolor.gif
Proposed Crosses (original):
Proposed Crosses (stage 2):
Final Crosses:
Wild type was dominant over all other eye colours (thus disproving our hypothesis that sepia would be dominant over all other eye colours), brown was dominant over sepia and white, and sepia was dominant over white. White was always recessive and was also the only sex-linked eye colour.
| Cross # | Parents | "Mendelian" Results | Our F1 Results |
|---|---|---|---|
| 1 | white female * wild male | 25 white -- all male 25 wild -- all female |
20 white -- all male 30 wild -- all female |
| 2 | white male * wild female | 25 wild -- female 25 wild -- male |
31 wild -- female 19 wild -- male |
| 3 | white female * brown male | 25 white -- all male 25 brown -- all female |
22 white -- all male 28 wild -- all female |
| 4 | white male * brown female | 25 brown -- female 25 brown -- male |
23 brown -- female 27 brown -- male |
| 5 | white female * sepia male | 25 white -- all male 25 sepia -- all female |
19 white -- 2 female, 17 male 31 sepia -- all female |
| 6 | white male * sepia female | 25 sepia -- female 25 sepia -- male |
24 sepia -- female 26 sepia -- male |
| 7 | sepia female * wild male | 25 wild -- female 25 wild -- male |
20 wild -- female 30 wild -- male |
| 8 | sepia male * wild female | 25 wild -- female 25 wild -- male |
18 wild -- female 32 wild -- male |
| 9 | sepia female * brown male | 25 brown -- female 25 brown -- male |
19 brown -- female 31 brown -- male |
| 10 | sepia male * brown female | 25 brown -- female 25 brown -- male |
23 brown -- female 27 brown -- male |
| 11 | brown female * wild male | 25 wild -- female 25 wild -- male |
21 wild -- female 29 wild -- male |
| 12 | brown male * wild female | 25 wild -- female 25 wild -- male |
27 wild -- female 23 wild -- male |
This chart compares the results of our F1 crosses with calculations based on patterns of inheritance studied by Mendel. These "Mendelian" crosses are calculated using Punnett squares, bearing in mind the actual dominant eye colour of each cross (not the hypothesized dominant eye colour) and whether the eye colours were sex-linked. Mendel, however, did not know about sex linkage, but we have calculated the numbers for the crosses involving white females with sex linkage factored in. Both categories are based on samples of fifty flies.
| Cross # | Parents | "Mendelian" Results | Our F2 Results |
|---|---|---|---|
| 1 | white female * wild male | (white) 12 female, 12 male (wild) 12 female, 12 male |
(white) 9 female, 14 male (wild) 17 female, 10 male |
| 2 | white male * wild female | (white) 6 female, 6 male (wild) 19 female, 19 male |
(white) 1 female, 11 male (wild) 14 female, 24 male |
| 3 | white female * brown male | (white) 12 female, 12 male (brown) 12 female, 12 male |
(white) 9 female, 12 male (brown) 13 female, 16 male |
| 4 | white male * brown female | (white) 6 female, 6 male (brown) 19 female, 19 male |
(white) 2 female, 13 male (brown) 15 female, 20 male |
| 5 | white female * sepia male | (white) 12 female, 12 male (sepia) 12 female, 12 male |
(white) 12 female, 12 male (sepia) 11 female, 15 male |
| 6 | white male * sepia female | (white) 6 female, 6 male (wild) 19 female, 19 male |
(white) 1 female, 12 male (wild) 12 female, 25 male |
| 7 | sepia female * wild male | (sepia) 6 female, 6 male (wild) 19 female, 19 male |
(sepia) 8 female, 7 male (wild) 10 female, 25 male |
| 8 | sepia male * wild female | (sepia) 6 female, 6 male (wild) 19 female, 19 male |
(sepia) 7 female, 10 male (wild) 15 female, 18 male |
| 9 | sepia female * brown male | (sepia) 6 female, 6 male (brown) 19 female, 19 male |
(sepia) 6 female, 8 male (brown) 19 female, 17 male |
| 10 | sepia male * brown female | (sepia) 6 female, 6 male (brown) 19 female, 19 male |
(sepia) 4 female, 6 male (brown) 12 female, 28 male |
| 11 | brown female * wild male | (brown) 6 female, 6 male (wild) 19 female, 19 male |
(brown) 4 female, 8 male (wild) 10 female, 28 male |
| 12 | brown male * wild female | (white) 6 female, 6 male (wild) 19 female, 19 male |
(white) 1 female, 11 male (wild) 14 female, 24 male |
This chart compares the results of our F2 crosses with calculations based on patterns of inheritance studied by Mendel. These "Mendelian" crosses are calculated using Punnett squares, bearing in mind the actual dominant eye colour of each cross (not the hypothesized dominant eye colour) and whether the eye colours were sex-linked. Mendel did not know about sex linkage, but we have calculated the numbers for the crosses involving white females with sex linkage factored in. Both categories are based on samples of fifty flies, however, in crosses involving a sex-linked eye colour, the numbers for the "Mendelian" crosses may be rounded down.