The larger mount of offspring allow for statistical analysis to be easy and reliable (Drosophila). Also the fact that their embryo grow outside the body allows for study of the organism at every stage. Another reason they are very popular for use is mutations can be easily targeted to specific genes. The life cycle of the flies is very simple and duration varies with according to temperature which is a characteristic of all cold- blooded insects (Sanitarian). The first stage of the cycle is egg form each egg is measured to be around 0. Mm a female can lay up to 400 eggs in favorable conditions. After hatch the Drosophila Melanomas goes through three instars stages as larvae. When the larvae has molted twice, it will have reached the third instars. The third instars now goes through a four day metamorphosis where it encapsulates itself inside a premium and arise as adults (Cassandra). For the experiment, a pair reciprocal did-hybrid cross was set up. My cross was between ebony (black body) males and vestigial (deformed, useless wings) females and the reciprocal cross between ebony females and vestigial males.
The purpose of this lab was to investigate whether the genes being tested were sex linked or autocross linked genes. Another purpose of the ABA was to determine whether the mutation was dominant or recessive between the genes. The way to asses that was to trace the heredity. Methods and Materials: To complete this experiment we used homozygous ebony and vestigial flies. We prepared the first medium between the two flies to obtain the reciprocal of the first cross. Provided to use in the lab were two fresh milk bottles. We added ml of Drosophila medium flakes (Carolina Biological) to each of them.
The Drosophila medium flakes are the food which the larvae will eat during their growth period. Then add ml of distilled water to complete the food and place 0 grains of yeast on the top which will be the food for the future adult flies. Once the medium was finished we labeled the bottle with the sex and phenotype (ebony and vestigial) of the flies along with each lab partner’s name. We collected the 10 ebony virgin and 10 Nan-virgin which was instructed to do also for the vestigial totaling at 40 flies. Flyway was used as anesthesia which we placed inside the vial for 1 to 2 minutes to transfer and count the flies.
Once the flies were put out to verify sex and phenotype and to count how many we put them on a white card, and used a microscope to get a better look. Once flies were rooted properly, we then placed those flies into a bottle making sure we sat the bottle on its side so until the flies woke up so they would not get stuck in medium. To keep the flies in the veil we used a sponge plug which also allowed for air to come through. To produce an IF generation we had to let the flies mate and lay eggs in the first cross and once the flies were done we would remove the adult flies and only keep the offspring from the Fl cross.
Once the offspring hatched, we could cross them which would give way to the IF cross. Always make sure to label your bottles so you could identified the Fl cross from the IF cross ND show the genotypes of the original parents. Results: In Bottle 1, Parental ebony males crossed with vestigial females produced an Fl generation that expressed only the wild type allele. In Bottle 2, Parental ebony females and vestigial males were crossed yielding an Fl generation of only wild type. Table 1. Wows the number of flies in the Parental Cross that resulted in the Fl generation from cross 1 of ebony males and vestigial females, and the reciprocal cross. The wild type fly was the only phenotype expressed. Cross 1 Total Female Fl Fl Total Wild type 69 85 154 60 72 132 Reciprocal Cross Table 2. Wows the number of flies counted and their phenotype of the IF generation when the Fl generations were self-fertilized. IF male IF Female IF Total IF Male Wild Type 156 201 357 181 216 397 Ebony 43 103 58 77 135 Vestigial 59 89 148 57 80 137 Discussion: e/e;VGA+/VGA+ x beg+ e +/e+,VGA/VGA e+/e;VGA+/VGA e+VGA Figure 1.
Homozygous Parental generations of ebony males (e/e;VGA+/VGA+) crossed with vestigial females (e+/e+;VGA/VGA) along with its reciprocal cross resulted in an all heterozygous Fl generation, having the same phenotypes and genotypes ratio expressing wild type allele. Beg e+VGA+ e/e;VGA/VGA e+/e;VGA/VGA e+/e;VGA+VGA e/e;VGA+VGA +/e;VGA+VGA+ x e+/e;VGA+/VGA e+/e+;VGA/VGA e+/e;VGA+/VGA+ e+/e+;VGA+/VGA Figure 2. Shows the theoretical results of the IF generation of both cross 1 and the reciprocal cross. It resulted in Mender’s typical 9:3:3:1 phenotypes ratio. /16 wild type, 3/16 ebony body, 3/16 vestigial wings, and 1/16 ebony body and vestigial wings. Table 3. Shows the Chi-squared analysis for the Fl generation of cross 1 Expected Ratio Observed Expected Deviation Deviations DO/e Total:132 Table 4. Shows the Chi-squared analysis table for the IF generation of cross 1. Expected Ratio 9/16 359 -2 4 0. 01 11 3/16 120 28 784 6. 533 -17 289 2. 408 1/16 30 0 -10 100 2. 5 Total: 638 11. 451 P z 0. 0001 Table 5. The Chi-squared for the Fl generation of the reciprocal cross. Expected Due Total: 154 Table 6.
The Chi-squared for the IF generation of the reciprocal cross. Expected 401 -4 16 0. 0399 134 0. 0075 3 9 0. 0671 45 0. 0227 Total: 713 XX – . 1372 p My data shows when Fl males and females were mated from cross 1 and the reciprocal cross, an IF generation consisting of wild type males and females, and ebony males and females, and vestigial were produced. Table 1 shows that only wild type flies were expressed and not any of the other trait, giving reason to think that the the wild type gene may be dominant. The result of data may be flawed from miscounts in fly counting and improper make up of the medium prepared for the flies food. The results of the Chi-squared analysis do not support the predicted hypothesis of a 9:3:3:1 phenotypes ratio of the IF generations.
This may be due to improper mathematics. The Chi-squared value for the Fl generation in both the first cross and reciprocal show that there was a 100% chance of expressing the wild type allele because it was zero. The The predicted 9:3:3:1 ratio of the IF generation of both crosses did not happen considering the actual data recorded in the laboratory. The high value of Chi-squared and low p value of both crosses suggests that a ratio was not achieved. The calculations in the Chi-squared analysis were skewed. The Chi-squared analysis rejects the hypothesis.
Conclusion: From the class data the five genes white, yellow, ebony, vestigial, and sepia were mapped. In the Fl generation of the first cross and reciprocal crosses involving white and yellow genes, only males expressed the gene, leaving all females expressing the wild type allele. White and yellow are located on the X- chromosome because they are sex-linked. There is no recombination occurring because the IF generation resulted in only parental gametes. Ebony and sepia are said to be on the same chromosome and are completely linked. Both the rental and recombinant gametes are produced, which proves complete linkage occurs.